Func Array Range Php Superglobals Filter Validate Boolean Func Ftp Set Option Pdo Begintransaction Func Array Natsort Php Preg_Split Func Mysqli Close Func Math Acos Func Http Headers Sent Func Directory Scandir Func Misc Connection Timeout Php Print_R Function Func Curl_Multi_Strerror Php Image Gd Func Filesystem Is File Func String Strrchr Func Array Sort Func Ftp Delete Func Filesystem Copy Func Curl_Multi_Remove_Handle Func Curl_Unescape Func Filesystem Clearstatcache Func Date Isodate Set Php Preg_Replace_Callback_Array Php Ref Timezones Func String Chr Func Cal Unixtojd Index Func Curl_Share_Close Func Filesystem Ftell Php Preg_Filter Func Math Hexdec Func String Ord Php Ref Libxml Php Xml Simplexml Func Filesystem Lstat Pdostatement Fetch Func String Substr Compare Func Filter Has Var Func Date Gettimeofday Php Imagecolorset Php Mysql Select Func Ftp Nb Put Func Array Slice Func Simplexml Attributes Php Debug_Zval_Dump Function Func Date Date Sub Php Mysql Insert Func Array Splice Pdo Exec Php Imagecolorstotal Func Date Sun Info Func Ftp Raw Php Post Func String Explode Filter Validate Booleant Php Imageaffinematrixget Func Date Date Set Php Restful Func Filesystem Pathinfo Php Is_Object Function Php Oop Func Array Next Func String Crc32 Func Date Time Php Ref Zip Func Mysqli Autocommit Func Array Uintersect Assoc Php Magic Constant Php Boolval Function Func Ftp Rename Php Get_Resource_Type Function Func String Nl Langinfo Func String Levenshtein Func Filesystem Chgrp Func String Strripos Php Mysql Intro Func Mysqli Data Seek Php Session Options Func Directory Readdir Func Array Values Func Mysqli Field Count Func Mysqli Select Db Func Xml Parser Free Func Mysqli Fetch Array Func Math Is Nan Func Cal Easter Date Func Date Default Timezone Set Func Filter Var Func Mysqli Set Charset Func Array Udiff Uassoc Func Curl_Multi_Init Func Array Replace Recursive Func Zip Entry Compressionmethod Func Zip Open Func Mysqli Get Connection Stats Func String Strtr Func Array Filter Func Cal Jdtounix Func Mysqli Connect Func Array Rsort Func String Strspn Func Zip Close Filter Sanitize Number Float Func String Echo Func Ftp Get Func String Substr Replace Func Ftp Exec Php Image Type To Mime Type Func String Strpos Func Math Lcg Value Func Array Search Func Xml Parser Create Func Ftp Mdtm Func Filesystem Stat Func Array Count Values Php Remove Sapi Pdostatement Errorcode Php Pdo Error Handling Func Array Uintersect Uassoc Func Curl_Setopt Func Directory Chdir Func String Join Func String Vfprintf Func String Convert Uudecode Func Curl_Multi_Info_Read Func Filesystem Filectime Func String Vprintf Func Xml Parse Into Struct Func Mail Mail Func String Convert Cyr String Func Simplexml Addchild Php Date Php Intval Function Func String Str Word Count Php Ref Mysqli Php Imagechar Func Zip Entry Close Func Filesystem Tempnam Func Mysqli Thread Safe Func String Strtok Func Mysqli Ping Func Filesystem Fgetc Func Array End Func Zip Read Php Ajax Xml Func Cal Frenchtojd Func Array Merge Pdostatement Setattribute Php Filtered Unserialize Func String Sscanf Func Xml Set Element Handler Func String Str Rot13 Func Cal Jewishtojd Func Simplexml Getname Php Imagecolorresolvealpha Php Is_String Function Func Array Key Php Tutorial Php7 New Features Func Filesystem Disk Free Space Func Array Diff Uassoc Php Ajax Rss Reader Func Math Base Convert Func Curl_Close Func Math Getrandmax Func Filesystem Is Uploaded File Func Curl_Multi_Exec Php Gettype Function Pdo Getavailabledrivers Func String Ltrim Func Array Usort Func String Md5 File Php Password_Needs_Rehash Php Imagecolorallocatealpha Func Filesystem Rmdir Func String Rtrim Func Misc Defined Php Install Filter Sanitize String Func Array Ksort Func Date Sunrise Func Simplexml Asxml Func Array Intersect Func Array In Array Func Array Combine Filter Validate Email Php Arrays Multi Func String Lcfirst Func Mysqli Error List Func String Strncasecmp Func Directory Getcwd Pdo Errorinfo Func Array Krsort Func Ftp Connect Php Cookies Func Date Timezone Location Get Func Misc Get Browser Func Cal Cal Info Php Mysql Prepared Statements Func Xml Get Current Line Number Func Mysqli Fetch Lengths Func Filesystem Dirname Func Mysqli Ssl Set Func Filesystem Is Writable Func String Quotemeta Func Date Mktime Func Array Unique Func Curl_Version Func Directory Closedir Php Datatypes Func Array Reverse Php Filter Php Xml Parser Expat Func Filter List Pdostatement Nextrowset Func Ftp Ssl Connect Func Mysqli Field Tell Func Xml Get Current Byte Index Func Filesystem Fputcsv Func String Quoted Printable Encode Func Simplexml Getnamespaces Func String Str Getcsv Pdostatement Bindvalue Php Ref Filesystem Php Mysql Where Func Mysqli Character Set Name Func Mysqli Errno Func Math Rand Func Mysqli Kill Func String Hex2Bin Func Misc Connection Status Pdostatement Fetchall Func Misc Sleep Php Imageantialias Func Date Timezone Set Func Curl_Reset Php Ref Math Func Date Date Create Func Mysqli Get Client Version Filter Validate Url Func Math Octdec Php Imagecreate Func Misc Show Source Func Math Sqrt Func Array Diff Func String Str Split Func Array Current Func Filesystem Rename Filter Validate Regexp Func Error Debug Print Backtrace Php Strval Function Func String Hebrev Func Ftp Mkdir Func Filesystem Parse Ini File Func Date Date Diff Func Ftp Nb Continue Func Misc Time Nanosleep Func Array Udiff Assoc Func Directory Rewinddir Func Mysqli Debug Func Ftp Nb Fget Php Mysql Connect Func Ftp Fput Php Error Handling Func Ftp Get Option Func Math Mt Rand Func Array Rand Pdostatement Rowcount Php Imagecolorclosestalpha Func Http Setrawcookie Func Mysqli Fetch Row Func String Stripslashes Func Mysqli Fetch Assoc Func Math Cosh Func String Strpbrk Php Mysql Create Table Php Forms Func Misc Highlight String Func String Strnatcasecmp Func Cal Jdtojulian Func Cal Jdtofrench Func Error Reporting Func Array Merge Recursive Func Array Key Last Func Array Php Imageaffinematrixconcat Func Cal Jdmonthname Php Echo Print Func Math Log10 Func String Strtoupper Func Filesystem File Get Contents Func Array Diff Ukey Func Libxml Clear Errors Func String Number Format Func Mysqli Get Server Version Func Array Intersect Ukey Func Math Acosh Pdostatement Bindparam Func Mysqli Info Php Get Func Math Atan Php Imagearc Php Is_Float Function Func Math Is Finite Func Cal Cal Days In Month Func Mysqli Real Escape String Func String Sprintf Func Mysqli Connect Errno Func Curl_Error Func Filesystem Chmod Func Mysqli Get Client Info Func Cal Cal From Jd Php Ref Filter Func Array Change Key Case Func Xml Utf8 Encode Func Curl_Multi_Add_Handle Func Misc Die Func String Print Php Ajax Poll Func Filesystem Unlink Php File Func Filesystem Filegroup Func Simplexml Registerxpathnamespace Func Filesystem Flock Func Math Bindec Func String Metaphone Func String Strip Tags Func Date Checkdate Func Math Round Func String Strncmp Php Form Url Email Php Imagecolortransparent Func String Html Entity Decode Func Array Arsort Func Filesystem Fclose Func Math Is Infinite Func Date Modify Func String Str Replace Php Is_Bool Function Php Coalescing Operator Php Is_Scalar Function Pdo Getattribute Php Csprng Func Mysqli Affected Rows Func String Strtolower Func Filesystem Ftruncate Func Filesystem Is Executable Func Error Restore Error Handler Func Filesystem Diskfreespace Func Math Asin Func Ftp Close Pdo Quote Php Is_Resource Function Php Is_Iterable Function Func Mysqli Error Php Variables Php Ref Http Func String Sha1 Func String Stripcslashes Php Var_Export Function Func Simplexml Load File Func Mysqli Query Func Filesystem Filesize Func Simplexml Xpath Func Cal Cal To Jd Func Misc Unpack Func Filesystem File Exists Php Syntax Func String Get Html Translation Table Func Filesystem Is Link Php Preg_Replace Func String Count Chars Func String Str Shuffle Func Array Compact Func Curl_Copy_Handle Php Empty Function Func Mysqli Connect Error Php Is_Numeric Function Php If Else Func Curl_Errno Php Is_Array Function Pdo Query Func Array Pop Func Xml Set Default Handler Php Ajax Php Func Mysqli More Results Func Mysqli Get Server Info Func Filesystem Fputs Pdostatement Debugdumpparams Func Filesystem Filemtime Func Ftp Alloc Php Ajax Database Php Ref Date Func Http Setcookie Func Misc Exit Php Unserialize Function Func Date Timestamp Set Func Curl_Share_Init Func Filesystem Fgets Php Spaceship Operator Func Array Column Func Filesystem Is Readable Func Mysqli Real Connect Func Mysqli Next Result Func Array Unshift Func Array Pad Php Imagealphablending Php Eof Heredoc Php Constant Arrays Php Ref Directory Func String Localeconv Func Error Log Func String Stripos Func Array Udiff Pdostatement Columncount Func Mysqli Insert Id Func Array Diff Key Func Misc Eval Func Array Uasort Func Mysqli Num Fields Func Math Exp Func Filesystem Fscanf Func Simplexml Import Dom Func String Mb_Substr Php Filter Advanced Func Filesystem Fileatime Func String Str Repeat Php Operators Func Mysqli Field Seek Php Arrays Php Mysql Create Pdo Errorcode Php Ref String Func Math Mt Srand Func String Similar Text Func Math Sinh Func Xml Set Notation Decl Handler Func String Ucwords Func Filesystem Fstat Php Sessions Php Get_Defined_Vars Function Func Filesystem Link Func Math Pow Func Array Product Func Mysqli Num Rows Func Mysqli Options Func Array Intersect Uassoc Php Form Validation Func String Mb_Strlen Func Error User Error Php Mysql Order By Func Cal Jdtogregorian Func Math Log1P Func Math Asinh Func Misc Strip Whitespace Func Mysqli Fetch Fields Func Mysqli Fetch Field Direct Func Filesystem Touch Func Ftp Size Func Error Restore Exception Handler Php Includes Func Ftp Pwd Func Math Decoct Func Ftp Login Func String Strrev Func Filesystem Chown Func Xml Set External Entity Ref Handler Func String Ucfirst Func Ftp Nb Get Func Simplexml Count Filter Sanitize Email Func Ftp Nlist Php Pdo Constants Func Directory Opendir Func Filesystem Fgetss Func Date Get Last Errors Php Imagecolorclosesthwb Pdostatement Closecursor Func Cal Juliantojd Func Simplexml Load String Php Anonymous Classes Func Xml Error String Php Password_Verify Func Array Shift Func Error Get Last Func String Str Ireplace Func String Quoted Printable Decode Func Date Strtotime Php Imagecolorclosest Php Scalar Return Type Func Mysqli Change User Func String Chop Func String Md5 Func Date Timestamp Get Func String Implode Func Array Count Func Math Tan Func Math Hypot Php Ref Calendar Filter Sanitize Stripped Func Filesystem Fnmatch Func Mysqli Refresh Func String Strcoll Func Mysqli Get Charset Php Imagecolorallocate Func Ftp Put Pdostatement Fetchcolumn Php Switch Php Preg_Match_All Func Array Map Func Zip Entry Compressedsize Php Image Type To Extension Func Date Timezone Identifiers List Func String Stristr Php Unset Function Func String Soundex Func String Substr Count Func Array Sizeof Php Use Statement Php Json Func String Wordwrap Pdostatement Errorinfo Func Math Ceil Func String Money Format Filter Validate Float Php Removed Extensions Func Filter Input Func Array Reduce Filter Sanitize Number Int Func Filesystem Fileperms Func Date Timezone Version Get Func Filesystem Fflush Func Array Fill Keys Func Filesystem Fileinode Func String Parse Str Func Mysqli Rollback Func Xml Parser Get Option Func Mysqli Fetch Object Func String Substr Php Is_Callable Function Func Xml Set Character Data Handler Func Math Mt Getrandmax Func Mysqli Fetch Field Filter Sanitize Special Chars Php Db Odbc Func Xml Get Current Column Number Func Date Timezone Get Func Cal Jdtojewish Php Expectations Func Filesystem Readlink Func Date Time Set Func String Strcmp Func Math Log Func Xml Get Error Code Php Closure Call Func Filesystem Fileowner Php Serialize Function Php Namespace Func Array Fill Func Libxml Use Internal Errors Func Filesystem Fwrite Func String Strlen Php Ref Error Func Math Sin Func Filesystem Mkdir Php Floatval Function Func String Strcspn Func Filesystem Filetype Php Constants Func Date Getdate Func String Addslashes Func Ftp Chdir Func Cal Easter Days Php Looping Php Arrays Sort Php Ref Misc Func Date Gmdate Func Filesystem Linkinfo Php Ajax Intro Pdo Intransaction Func Filesystem Is Writeable Php Ref Array Func String Hebrevc Func Misc Highlight File Func Date Timezone Name From Abbr Func Math Expm1 Filter Callback Func Xml Utf8 Decode Func Misc Define Pdo Setattribute Func Math Tanh Func Filesystem Set File Buffer Func Filesystem Fgetcsv Func Filesystem Fseek Php Mail Func Math Pi Pdo Commit Php Getimagesize Func String Crypt Func Array Asort Func Date Sunset Php Xml Dom Func Mysqli Fetch All Func Filesystem Rewind Func Math Srand Func Array Prev Func Mysqli Stat Func String Htmlspecialchars Func Math Atanh Php Preg_Quote Func Date Date Func Simplexml Addattribute Filter Sanitize Url Func Date Gmmktime Pdo Construct Php Pdo Func Curl_Multi_Setopt Func String Nl2Br Php Settype Function Func String Vsprintf Php Imageaffine Func Ftp Chmod Func Math Fmod Func Error Set Exception Handler Func Array Diff Assoc Php Ref Curl Func String Strchr Func Date Timezone Abbreviations List Func Ftp Site Php Imagecharup Php Ajax Livesearch Func Math Cos Pdostatement Fetchobject Php Form Complete Func Date Timezone Open Func Http Headers List Func Ftp Cdup Func Mysqli Commit Func Math Deg2Rad Func String Bin2Hex Php Functions Func Date Localtime Func Filesystem Fpassthru Func Math Rad2Deg Php File Upload Func String Fprintf Php Imagecolorat Func Date Microtime Php Intro Func Date Create From Format Func Curl_Escape Func Date Date Parse Func Curl_Init Func Filesystem Fread Func Http Header Func Filesystem Pclose Func String Sha1 File Func Xml Set Object Func Misc Constant Php Getimagesizefromstring Func Date Strftime Func Math Abs Php Password_Hash Php Imagecolormatch Func Simplexml Children Php Looping For Func Mysqli Thread Id Func Filesystem Is Dir Func Filesystem Umask Func Array Multisort Func Misc Time Sleep Until Func Math Dechex Func Curl_Strerror Func String Strnatcmp Func Misc Connection Aborted Php Secure Mail Func Filesystem Move Uploaded File Php Var_Dump Function Php Pcre Func Date Timezone Name Get Php Pdo Connections Func Array Reset Func String Setlocale Php Intlchar Filter Sanitize Magic Quotes Func Filesystem Glob Func Mysqli Get Host Info Php Ref Xml Func Date Offset Get Php Pdo Lobs Func Ftp Rmdir Func Ftp Nb Fput Php Imagesx Imagesy Func Ftp Fget Func Mysqli Get Client Stats Filter Sanitize Encoded Func Array Pos Func String Addcslashes Php Is_Int Function Php Pdo Transactions Func Array Intersect Assoc Func Misc Usleep Php Imagecolorexact Func Filesystem File Put Contents Func Array Intersect Key Func Mysqli Stmt Init Filter Validate Int Func Zip Entry Read Func Filesystem Popen Php Ref Ftp Func String Strrpos Func Xml Parser Create Ns Php Intdiv Func Date Gmstrftime Func Filesystem Readfile Func String Printf Func Math Atan2 Func Simplexml Construct Func Curl_Setopt_Array Pdo Lastinsertid Php String Func Xml Set Processing Instruction Handler Func Curl_File_Create Php Preg_Replace_Callback Php Imagecolorexactalpha Func Array Sum Func Error Trigger Error Func String Chunk Split Func Date Date Format Func Date Strptime Php Mysql Insert Multiple Func Mysqli Sqlstate Func Curl_Pause Func Simplexml Getdocnamespaces Php Curl Func Date Interval Format Func Array Each Php Is_Null Function Func Array Keys Php Pdo Prepared Statements Func Date Timezone Offset Get Func String Trim Func Filesystem Tmpfile Func Ftp Rawlist Func Array Key Exists Func Array Key First Func Filesystem Feof Func Directory Dir Func String Str Pad Func String Htmlspecialchars Decode Func Array Extract Func Date Date Add Php Deprecated Features Php Ref Mail Php Error Pdostatement Execute Pdostatement Setfetchmode Func Mysqli Init Func Array List Php Mysql Delete Func Curl_Share_Setopt Php Import_Request_Variables Function Php Types Comparisons Func Zip Entry Filesize Php Variable Handling Functions Func Filesystem Realpath Php Preg_Last_Error Php Password_Get_Info Func Zip Entry Open Func Misc Ignore User Abort Func Directory Chroot Filter Validate Ip Func Array Uintersect Php Isset Function Func Array Natcasesort Pdo Prepare Func Array Replace Pdo Rollback Php Mysql Update Func Curl_Exec Func Curl_Multi_Getcontent Func Array Walk Func Filesystem Symlink Func Misc Uniqid Func Ftp Pasv Php Form Required Func String Convert Uuencode Func Filesystem Fopen Func Cal Gregoriantojd Pdostatement Getattribute Func Date Idate Func Curl_Multi_Select Func Ftp Quit Func Error Set Error Handler Func Array Uksort Func Array Push Func Filesystem File Func Zip Entry Name Func Filter Var Array Func Ftp Systype Func Mail Ezmlm_Hash Func Math Floor Func Array Chunk Pdostatement Getcolumnmeta Php Preg_Match Func Xml Parser Set Option Func Filter Input Array Func Math Min Func Math Max Func Filesystem Basename Php Imagecolordeallocate Php Ref Simplexml Func Xml Parse Func String Strstr Func Curl_Multi_Close Func Array Walk Recursive Func Curl_Getinfo Php Image2Wbmp Func Error Debug Backtrace Filter Unsafe Raw Func Date Default Timezone Get Php Imagecolorsforindex Php Exception Func String Strcasecmp Func Misc Pack Func Array Shuffle Func Mysqli Free Result Func Mysqli Get Proto Info Func Filter Id Func Libxml Get Last Error Func Filesystem Disk Total Space Func Mysqli Dump Debug Info Func Array Flip Func Cal Jddayofweek Php Preg_Grep Func Libxml Get Errors Func String Htmlentities Php Gd Info Func Date Parse From Format Func Xml Set Unparsed Entity Decl Handler Func Math Decbin Pdostatement Bindcolumn Func Mysqli Multi Query

bool isset ( mixed $var [, mixed $... ] )

<?php
$var = '';

// The result is TRUE, so the text will be printed.
if (isset($var)) {
    echo "Variable is set." . PHP_EOL;
}

// In the following examples, we will use var_dump to output the return value of isset().

$a = "test";
$b = "anothertest";

var_dump(isset($a));      // TRUE
var_dump(isset($a, $b)); // TRUE

unset ($a);

var_dump(isset($a));     // FALSE
var_dump(isset($a, $b)); // FALSE

$foo = NULL;
var_dump(isset($foo));   // FALSE
?>

Variable is set.
bool(true)
bool(true)
bool(false)
bool(false)
bool(false)

<?php
$a = array ('test' => 1, 'hello' => NULL, 'pie' => array('a' => 'apple'));

var_dump(isset($a['test']));            // TRUE
var_dump(isset($a['foo']));             // FALSE
var_dump(isset($a['hello']));           // FALSE

// The key 'hello' is equal to NULL, so it is considered unset.
// To check for NULL key values, you can use the following method.
var_dump(array_key_exists('hello', $a)); // TRUE

// Deeper level check
var_dump(isset($a['pie']['a']));        // TRUE
var_dump(isset($a['pie']['b']));        // FALSE
var_dump(isset($a['cake']['a']['b']));  // FALSE
?>

bool(true)
bool(false)
bool(false)
bool(true)
bool(true)
bool(false)
bool(false)

<?php
$expected_array_got_string = 'somestring';
var_dump(isset($expected_array_got_string['some_key']));
var_dump(isset($expected_array_got_string[0]));
var_dump(isset($expected_array_got_string['0']));
var_dump(isset($expected_array_got_string[0.5]));
var_dump(isset($expected_array_got_string['0.5']));
var_dump(isset($expected_array_got_string['0 Mostel']));
?>

bool(true)
bool(true)
bool(true)

Output of the above example in PHP 5.4: