Php find in array functions

PHP in_array

Summary: in this tutorial, you will learn how to use the PHP in_array() function to check if a value exists in an array.

Introduction to the PHP in_array() function

The in_array() function returns true if a value exists in an array. Here’s the syntax of the in_array() function:

in_array ( mixed $needle , array $haystack , bool $strict = false ) : boolCode language: PHP (php)

• $needle is the searched value.
• $haystack is the array to search.
• $strict if the $strict sets to true , the in_array() function will use the strict comparison.

The in_array() function searches for the $needle in the $haystack using the loose comparison ( == ). To use the strict comparison ( === ), you need to set the $strict argument to true .

If the value to check is a string, the in_array() function will search for it case-sensitively.

The in_array() function returns true if the $needle exists in the $array ; otherwise, it returns false .

PHP in_array() function examples

Let’s take some examples of using the in_array() function.

1) Simple PHP in_array() function examples

The following example uses the in_array() function to check if the value ‘update’ is in the $actions array:

 $actions = [ 'new', 'edit', 'update', 'view', 'delete', ]; $result = in_array('update', $actions); var_dump($result); // bool(true)Code language: HTML, XML (xml)

The following example returns false because the publish value doesn’t exist in the $actions array:

 $actions = [ 'new', 'edit', 'update', 'view', 'delete', ]; $result = in_array('publish', $actions); var_dump($result); // bool(false) Code language: HTML, XML (xml)

The following example returns false because the value ‘New’ doesn’t exist in the $actions array. Note that the in_array() compares the strings case-sensitively:

 $actions = [ 'new', 'edit', 'update', 'view', 'delete', ]; $result = in_array('New', $actions); var_dump($result); // bool(false) Code language: HTML, XML (xml)

2) Using PHP in_array() function with the strict comparison example

The following example uses the in_array() function to find the number 15 in the $user_ids array. It returns true because the in_array() function compares the values using the loose comparison ( == ):

 $user_ids = [10, '15', '20', 30]; $result = in_array(15, $user_ids); var_dump($result); // bool(true)Code language: HTML, XML (xml)

To use the strict comparison, you pass false to the third argument ( $strict ) of the in_array() function as follows:

 $user_ids = [10, '15', '20', 30]; $result = in_array(15, $user_ids, true); var_dump($result); // bool(false)Code language: HTML, XML (xml)

This time the in_array() function returns false instead.

3) Using PHP in_array() function with the searched value is an array example

The following example uses the in_array() function with the searched value is an array:

 $colors = [ ['red', 'green', 'blue'], ['cyan', 'magenta', 'yellow', 'black'], ['hue', 'saturation', 'lightness'] ]; if (in_array(['red', 'green', 'blue'], $colors)) < echo 'RGB colors found'; > else < echo 'RGB colors are not found'; >Code language: HTML, XML (xml)

4) Using PHP in_array() function with an array of objects example

The following defines the Role class that has two properties $id and $name :

 class Role < private $id; private $name; public function __construct($id, $name) < $this->id = $id; $this->name = $name; > >Code language: HTML, XML (xml)

This example illustrates how to use the in_array() function to check if a Role object exists in an array of Role objects:

 // Role class $roles = [ new Role(1, 'admin'), new Role(2, 'editor'), new Role(3, 'subscribe'), ]; if (in_array(new Role(1, 'admin'), $roles)) < echo 'found it'; >Code language: HTML, XML (xml)

If you set the $strict to true , the in_array() function will compare objects using their identities instead of values. For example:

// Role class $roles = [ new Role(1, 'admin'), new Role(2, 'editor'), new Role(3, 'subscribe'), ]; if (in_array(new Role(1, 'admin'), $roles, true)) < echo 'found it!'; > else < echo 'not found!'; >Code language: PHP (php)

Summary

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in_array

Searches for needle in haystack using loose comparison unless strict is set.

Parameters

Note:

If needle is a string, the comparison is done in a case-sensitive manner.

If the third parameter strict is set to true then the in_array() function will also check the types of the needle in the haystack .

Note:

Prior to PHP 8.0.0, a string needle will match an array value of 0 in non-strict mode, and vice versa. That may lead to undesireable results. Similar edge cases exist for other types, as well. If not absolutely certain of the types of values involved, always use the strict flag to avoid unexpected behavior.

Return Values

Returns true if needle is found in the array, false otherwise.

Examples

Example #1 in_array() example

$os = array( «Mac» , «NT» , «Irix» , «Linux» );
if ( in_array ( «Irix» , $os )) echo «Got Irix» ;
>
if ( in_array ( «mac» , $os )) echo «Got mac» ;
>
?>

The second condition fails because in_array() is case-sensitive, so the program above will display:

Example #2 in_array() with strict example

if ( in_array ( ‘12.4’ , $a , true )) echo «‘12.4’ found with strict check\n» ;
>

if ( in_array ( 1.13 , $a , true )) echo «1.13 found with strict check\n» ;
>
?>

The above example will output:

1.13 found with strict check

Example #3 in_array() with an array as needle

if ( in_array (array( ‘p’ , ‘h’ ), $a )) echo «‘ph’ was found\n» ;
>

if ( in_array (array( ‘f’ , ‘i’ ), $a )) echo «‘fi’ was found\n» ;
>

if ( in_array ( ‘o’ , $a )) echo «‘o’ was found\n» ;
>
?>

The above example will output:

See Also

• array_search() — Searches the array for a given value and returns the first corresponding key if successful
• isset() — Determine if a variable is declared and is different than null
• array_key_exists() — Checks if the given key or index exists in the array

User Contributed Notes 8 notes

Loose checking returns some crazy, counter-intuitive results when used with certain arrays. It is completely correct behaviour, due to PHP’s leniency on variable types, but in «real-life» is almost useless.

The solution is to use the strict checking option.

$array = array(
‘egg’ => true ,
‘cheese’ => false ,
‘hair’ => 765 ,
‘goblins’ => null ,
‘ogres’ => ‘no ogres allowed in this array’
);

// Loose checking — return values are in comments

// First three make sense, last four do not

in_array ( null , $array ); // true
in_array ( false , $array ); // true
in_array ( 765 , $array ); // true
in_array ( 763 , $array ); // true
in_array ( ‘egg’ , $array ); // true
in_array ( ‘hhh’ , $array ); // true
in_array (array(), $array ); // true

in_array ( null , $array , true ); // true
in_array ( false , $array , true ); // true
in_array ( 765 , $array , true ); // true
in_array ( 763 , $array , true ); // false
in_array ( ‘egg’ , $array , true ); // false
in_array ( ‘hhh’ , $array , true ); // false
in_array (array(), $array , true ); // false

I got an unexpected behavior working with in_array. I’m using following code:

// .
$someId = getSomeId (); // it gets generated/fetched by another service, so I don’t know what value it will have. P.S.: it’s an integer

// The actual data in my edge-case scenario:
// $someId = 0;
// $anyArray = [‘dataOne’, ‘dataTwo’];
if ( in_array ( $someId , $anyArray )) // do some work
>
// .
?>

With PHP7.4, in_array returns boolean true.
With PHP8.1, in_array returns boolean false.

It took me quite some time to find out what’s going on.

I found out that in_array will *not* find an associative array within a haystack of associative arrays in strict mode if the keys were not generated in the *same order*:

$needle = array(
‘fruit’ => ‘banana’ , ‘vegetable’ => ‘carrot’
);

$haystack = array(
array( ‘vegetable’ => ‘carrot’ , ‘fruit’ => ‘banana’ ),
array( ‘fruit’ => ‘apple’ , ‘vegetable’ => ‘celery’ )
);

echo in_array ( $needle , $haystack , true ) ? ‘true’ : ‘false’ ;
// Output is ‘false’

echo in_array ( $needle , $haystack ) ? ‘true’ : ‘false’ ;
// Output is ‘true’

?>

I had wrongly assumed the order of the items in an associative array were irrelevant, regardless of whether ‘strict’ is TRUE or FALSE: The order is irrelevant *only* if not in strict mode.

I’d like to point out that, if you’re using Enum data structures and want to compare whether an array of strings has a certain string Enum in it, you need to cast it to a string.

From what I’ve tested, the function works correctly:
if the array is filled with strings and you’re searching for a string;
if the array is filled with Enums and you’re searching for an Enum.

Here is a recursive in_array function:

$myNumbers = [
[ 1 , 2 , 3 , 4 , 5 ],
[ 6 , 7 , 8 , 9 , 10 ],
];

$array = [
‘numbers’ => $myNumbers
];

// Let’s try to find number 7 within $array
$hasNumber = in_array ( 7 , $array , true ); // bool(false)
$hasNumber = in_array_recursive ( 7 , $array , true ); // bool(true)

function in_array_recursive ( mixed $needle , array $haystack , bool $strict ): bool
foreach ( $haystack as $element ) if ( $element === $needle ) return true ;
>

$isFound = false ;
if ( is_array ( $element )) $isFound = in_array_recursive ( $needle , $element , $strict );
>

if ( $isFound === true ) return true ;
>
>

If you’re creating an array yourself and then using in_array to search it, consider setting the keys of the array and using isset instead since it’s much faster.

$slow = array( ‘apple’ , ‘banana’ , ‘orange’ );

if ( in_array ( ‘banana’ , $slow ))
print( ‘Found it!’ );

$fast = array( ‘apple’ => ‘apple’ , ‘banana’ => ‘banana’ , ‘orange’ => ‘orange’ );

if (isset( $fast [ ‘banana’ ]))
print( ‘Found it!’ );

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