PHP Exercises: Check if a given string begins with 'abc' or 'xyz'

Last update on May 28 2025 13:04:57 (UTC/GMT +8 hours)

79. Check String Starts with 'abc' or 'xyz'

Write a PHP program to check if a given string begins with 'abc' or 'xyz'. If the string begins with 'abc' or 'xyz' return 'abc' or 'xyz' otherwise return the empty string.

Sample Solution:

PHP Code :

<?php
// Define a function named 'test' that checks the prefix of a string
function test($s1)
{ 
    // Check if the first three characters of $s1 are "abc"
    if (substr($s1, 0, 3) == "abc")
    {
        // If true, return "abc"
        return "abc";
    }
    // Check if the first three characters of $s1 are "xyz"
    else if (substr($s1, 0, 3) == "xyz")
    {
        // If true, return "xyz"
        return "xyz";
    }
    // If the conditions are not met, return an empty string
    else
    {
        return "";
    }
}

// Test the 'test' function with different strings, then display the results using echo
echo test("abc")."\n";
echo test("abcdef")."\n";
echo test("C")."\n";
echo test("xyz")."\n";
echo test("xyzsder")."\n";
?>

Explanation:

Function Definition:

The function test is defined with one parameter:

$s1: the input string to check.

Prefix Check (First Condition):

The function checks if the first three characters of $s1 are "abc":

if (substr($s1, 0, 3) == "abc")

If true:

It returns the string "abc".

Prefix Check (Second Condition):

If the first condition is false, it checks if the first three characters of $s1 are "xyz":

else if (substr($s1, 0, 3) == "xyz")

If true:

It returns the string "xyz".

Default Return Value:

If neither condition is met:

It returns an empty string "".

Output:

abc
abc

xyz
xyz

Flowchart:

For more Practice: Solve these Related Problems:

Write a PHP script to determine if a string begins with "abc" or "xyz" and return the matching prefix, or an empty string otherwise.
Write a PHP function to scan the start of a string for either "abc" or "xyz" and output the detected substring.
Write a PHP program to check a string's prefix and return it if it equals one of the two target values using substring comparison.
Write a PHP script to use regex to match the beginning of the string with either "abc" or "xyz" and output the match accordingly.

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PHP Code Editor:

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