Check if String is Boolean in PHP

This tutorial will discuss multiple ways to check if string is boolean in PHP.

Table Of Contents

Method 1: Using strict comparison

To check if a string contains a boolean value, we can follow these steps:

First, we need to convert the given string to lowercase using the strtolower() function. This ensures case-insensitive comparison. Then, we check if the lowercase string is equal to either “true” or “false”. If it matches either of these values, it means that the string contains a boolean value.

We have created a separate function for this purpose.

function isBooleanString($strValue)
{
    return  strtolower($strValue) === 'true' ||
            strtolower($strValue) === 'false';
}

It accepts a string as an argument and returns true if the given string is a boolean value.

Let’s see the complete example,

<?php
/**
 * Check if a string represents a boolean value.
 *
 * @param string $strValue The string to validate.
 * @return bool True if the string represents a boolean value, false otherwise.
 */
function isBooleanString($strValue)
{
    return  strtolower($strValue) === 'true' ||
            strtolower($strValue) === 'false';
}

$strValue = 'true';

// Check if string contains a Valid Boolean Value
if (isBooleanString($strValue)) {
    echo "The string represents a boolean value.";
} else {
    echo "The string does not represent a boolean value.";
}
?>

Output

The string represents a boolean value.

Method 2: Using filter_var() function

We can also use the filter_var() function with the FILTER_VALIDATE_BOOLEAN filter. By passing the string as the first argument and FILTER_VALIDATE_BOOLEAN as the second argument, the function will return true if the string contains a boolean value.

Let’s see the complete example,

<?php
/**
 * Check if a string represents a boolean value.
 *
 * @param string $strValue The string to validate.
 * @return bool True if the string represents a boolean value, false otherwise.
 */
function isBoolean($strValue)
{
    return filter_var(
                $strValue,
                FILTER_VALIDATE_BOOLEAN,
                FILTER_NULL_ON_FAILURE) !== null;
}

$strValue = 'false';

// Check if string contains a Valid Boolean Value
if (isBoolean($strValue)) {
    echo "The string represents a boolean value.";
} else {
    echo "The string does not represent a boolean value.";
}
?>

Output

The string represents a boolean value.

Summary

Today, we learned about multiple ways to check if string is boolean in PHP.