Categorized | Code

Creating a Character Sequence In PHP

Note: Before you read this, read the edit at the bottom.

Recently I needed to created a character sequence in PHP like this: aa, ab, ac and so forth. The range() function can’t handle multiple characters, so I wrote a function to generate the next string in the sequence based on the string sent in. The function “carries the one”, so to speak, meaning the next string after az is ba. After zz comes aa again. You can use any amount of characters, so aaaa will yield aaab.

function get_next_in_sequence($str) {
	$letters = range('a', 'z');
	$arr = str_split($str);
	// Replace each character with numeric equivalent
	foreach ($arr as $key => $char) {
		$arr[$key] = array_search($char, $letters); 
	}
	$digits = count($arr)-1; // Count digits
	for ($i=$digits; $i > -1; $i--) { // Starting at the right-most spot, move left
		if ($i == $digits) // If this is the right most spot
			$arr[$i]++; // Increment it
		if ($arr[$i] == 26) { // If this spot has moved past "z"
			$arr[$i] = 0;	// Set it to "a"
			if ($i != 0) // Unless it is the left most spot
				$arr[$i-1]++;  // Carry the one to the next spot
		} 
	}
	// Rebuild characters from numeric equivalent
	foreach ($arr as $key => $char) { 
		$arr[$key] = $letters[$char];
	}
	$str = implode($arr);
	return $str;
}

CRUTIAL EDIT:

Thanks to a helpful comment from Daniel, it has been brought to my attention that this is now unnecessary. Use this instead:

http://php.net/language.operators.increment.php

Thanks Daniel!

This post was written by:

- who has written 36 posts on whit.info.


2 Responses to “Creating a Character Sequence In PHP”

  1. Daniel says:

    I was looking for the same thing and I found your code but I then found a simpler solution:

    $i=’a';
    echo ++$i; // ‘b’

    $i=’z';
    echo ++$i; // ‘aa’

    Documented here:
    php.net/language.operators.increment.php

    Cheers,

    Daniel

  2. Whit Nelson says:

    Right you are. Thanks very much! I’ve update the post to reflect this.

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