Check if String is an Integer in PHP

This tutorial will discuss about a unique way to check if string is an integer in php.

To check if a string contains only an integer, we can use the is_numeric() function in PHP. It accepts a variable as an argument and returns true, if the given variable is either numeric or a string containing numeric value. But if the variable is not set yet, then in that case it will still return true. So we need to use the ctype_digit() function along with the is_numeric() function.

The ctype_digit() function accept a string as an argument, and returns true if the all the characters in the given string are digits.

So, we can use a combination of both the methods i.e. is_numeric($str) && ctype_digit($str), to check if given string is in valid integer or not.

For this, we have created a separate function i.e.

function isIntegerString($str)
{
    return  is_numeric($str) &&
            ctype_digit($str);
}

It accepts a string as an argument and returns true if the given string is a valid integer.

Let’s see the complete example,

<?php
/**
 * Checks if a string represents a valid integer
 * using is_numeric() and ctype_digit().
 *
 * @param string $str The string to check.
 * @return bool True if the string represents a valid integer, false otherwise.
 */
function isIntegerString($str)
{
    return  is_numeric($str) &&
            ctype_digit($str);
}

$strValue = "956";

// Check if string is a valid integer
if (isIntegerString($strValue)) {
    echo "The string represents a valid integer.";
} else {
    echo "The string does not represent a valid integer.";
}
?>

Output

The string represents a valid integer.

Summary

We learned a way to check if a string contains an integer only in PHP.