PHP Exercises: Test if a given string occurs at the end of another given string

Last update on December 20 2024 10:17:55 (UTC/GMT +8 hours)

Write a PHP program to test if a given string occurs at the end of another given string.

Sample Solution:

PHP Code:

<?php
// Function to check if str2 is at the end of str1
function str2_in_str1($str1, $str2) {
    // Calculate the length of str2
    $p_len = strlen($str2);
    // Calculate the length of str1
    $w_len = strlen($str1);
    // Calculate the starting index for str2 in str1
    $w_start = $w_len - $p_len - 1;

    // Check if the substring at the calculated index in str1 is equal to str2
    if (substr($str1, $w_len - $p_len, $p_len) == $str2) {
        return "true";
    } else {
        return "false";
    }
}

// Example usage with different strings
echo str2_in_str1("Python", "on") . "\n";        // Output: true
echo str2_in_str1("JavaScript", "php") . "\n";   // Output: false

?>

Explanation:

Function Definition:

The function str2_in_str1($str1, $str2) checks if the string $str2 appears at the end of the string $str1.

Calculate Lengths:

$p_len stores the length of $str2.
$w_len stores the length of $str1.

Determine Starting Index:

$w_start calculates the index where $str2 should start in $str1 if it appears at the end. This is calculated by subtracting $p_len from $w_len.

Check if End of $str1 Matches $str2:

substr($str1, $w_len - $p_len, $p_len) extracts the substring from $str1 that has the same length as $str2 and starts at the calculated position.
If this substring matches $str2, the function returns "true", indicating $str2 is at the end of $str1; otherwise, it returns "false".

Example Usage:

The function is tested with "Python", "on" (returns "true") and "JavaScript", "php" (returns "false"), and the results are printed.

Output:

true                                                        
false

Flowchart:

PHP Code Editor:

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