How to check if a string is in an array using php

In PHP development, querying whether a string is in an array is a very common operation. In this article, we will explore some methods to check if a string is in a PHP array.

Method 1: Use the in_array() function

The in_array() function in PHP is used to check whether a value exists in an array. We can use this function to find whether a string is in an array:

$array = array('apple', 'banana', 'orange', 'grape');

if (in_array('banana', $array)) {
    echo 'Found';
} else {
    echo 'Not Found';
}

This code will output: Found. Because 'banana' exists in the array.

Let's change it to search for another string 'watermelon':

$array = array('apple', 'banana', 'orange', 'grape');

if (in_array('watermelon', $array)) {
    echo 'Found';
} else {
    echo 'Not Found';
}

This code will output: Not Found, because 'watermelon' is not in the array.

Method 2: Using the array_search() function

Now, let’s look at another way to find whether a string is in a PHP array. Use the array_search() function:

$array = array('apple', 'banana', 'orange', 'grape');

if (array_search('banana', $array)) {
    echo 'Found';
} else {
    echo 'Not Found';
}

This code will output: Found. Because 'banana' exists in the array.

Let's change it to search for another string 'watermelon':

$array = array('apple', 'banana', 'orange', 'grape');

if (array_search('watermelon', $array)) {
    echo 'Found';
} else {
    echo 'Not Found';
}

This code will output: Not Found, because 'watermelon' is not in the array.

Method 3: Use in_array() and strtolower() functions

In the above two methods, we did not consider the case issue. So the following method ignores case:

$array = array('Apple', 'Banana', 'Orange', 'Grape');

$search_term = 'banana';

if (in_array(strtolower($search_term), array_map('strtolower', $array))) {
    echo 'Found';
} else {
    echo 'Not Found';
}

Use the array_map() function to process the string traversing the entire array, use the strtolower() function to convert the string to lowercase and store it in a new array middle. We can then use the in_array() function to find whether the specified string is in the new array.

If we instead search for another string such as 'Watermelon':

$array = array('Apple', 'Banana', 'Orange', 'Grape');

$search_term = 'Watermelon';

if (in_array(strtolower($search_term), array_map('strtolower', $array))) {
    echo 'Found';
} else {
    echo 'Not Found';
}

This outputs Not Found because there is no string in the new array that matches 'Watermelon'.

At this point, we have mastered three different methods in PHP to check whether a string exists in an array. From a performance perspective, the in_array() function and array_search() function seem to be more efficient and do not involve traversing the entire array elements.

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