How to Check If a Number Exists in an Array in PHP? Four Common Methods Explained

How to Check If a Number Exists in an Array in PHP?

In PHP, you can use different functions and loop structures to check if a number exists in an array. Below, we will introduce several common methods to achieve this.

Using in_array Function

PHP provides the in_array() function to check whether an element exists in an array. The function takes two parameters: the element to search for and the target array.

$number = 5;
$array = [1, 3, 5, 7, 9];
if (in_array($number, $array)) {
    echo "Number {$number} exists in the array";
} else {
    echo "Number {$number} does not exist in the array";
}

In the example above, we use the in_array() function to check if $number exists in the $array. If it does, we output a message saying the number exists in the array; otherwise, we output a message saying it does not exist in the array.

Using array_search Function to Check and Return Key Name

In addition to in_array(), PHP also provides the array_search() function, which checks if an element exists in an array and returns the key of that element.

$number = 5;
$array = [1, 3, 5, 7, 9];
$key = array_search($number, $array);
if ($key !== false) {
    echo "Number {$number} exists in the array, with key {$key}";
} else {
    echo "Number {$number} does not exist in the array";
}

In this example, the array_search() function returns the index of $number in $array. When $key is not equal to false, it means the number exists in the array, and we output the key name; otherwise, we output a message saying the number does not exist in the array.

Combining in_array and array_search to Get Number and Index

You can also combine in_array() and array_search() to check if a number exists in the array and retrieve its index value.

$number = 5;
$array = [1, 3, 5, 7, 9];
if (in_array($number, $array)) {
    $key = array_search($number, $array);
    echo "Number {$number} exists in the array, with index {$key}";
} else {
    echo "Number {$number} does not exist in the array";
}

In this case, we first use the in_array() function to check if $number exists in $array. If it does, we use the array_search() function to return the index value and output it. If the number does not exist, we output a message indicating that.

Using foreach Loop to Iterate through the Array

In addition to built-in array functions, we can also use a foreach loop to iterate through the array and manually check if the number exists in the array.

$number = 5;
$array = [1, 3, 5, 7, 9];
$found = false;
foreach ($array as $key => $value) {
    if ($value == $number) {
        $found = true;
        echo "Number {$number} exists in the array, with index {$key}";
        break;  // Exit the loop once the number is found
    }
}
if (!$found) {
    echo "Number {$number} does not exist in the array";
}

In this example, we iterate through the $array using a foreach loop and check if each element equals $number. If a match is found, we output a message saying the number exists in the array and display its index. If no match is found, we output a message saying the number does not exist in the array.

Summary

These are several common methods to check if a number exists in an array in PHP. Depending on your needs, you can use in_array(), array_search(), or a foreach loop to achieve this.

By using these methods, you can easily check if a number exists in an array and take further actions as needed.