PHP – Check if Array Key Exists

In PHP, we can check if a specific key exists in an array using the array_key_exists() function which is a built in function in PHP or by using another built in  isset() function. Here’s how you can use both methods:

Method 1: Using array_key_exists() function

array_key_exists() function is a built-in PHP function used to check if a specific key exists in an array. It takes two parameters: the key we want to check for, and the array we want to search in. The function returns true if the key exists in the array, and false if the key doesn’t exist in the array.

<?php
// define or make the array
$students = array(
    'name' => 'John Doe',
    'roll' => '101',
    'class' => '9'
);

// Using array_key_exists()
if (array_key_exists('roll', $students)) {
    echo "Key 'roll' exists in the array.";
} else {
    echo "Key 'roll' does not exist in the array.";
}

echo "<br>";
?>

Method 2: Using isset() function

The isset() function is a widely used function in PHP. The isset() function in PHP is used to determine if a variable is set and is not NULL. It returns true if the variable exists and has a value other than NULL, and false otherwise. This function can accept multiple parameters, and it checks each parameter separately.

<?php

// Using isset() function

define or make the array 
$students = array( 
'name' => 'John Doe', 
'roll' => '101', 
'class' => '9' 
);

if (isset($students['class'])) 
{ 
    echo "Key 'class' exists in the array."; 
} 
else { 
    echo "Key 'class' does not exist in the array."; 
} 
?>

Both methods example output will output that the array key exists in out cases.

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