Loop chars

Suppose we have a string with some characters in it. In PHP programs, it is often necessary to loop over and test these characters in some way.

With for and foreach, we can access the characters in a string. But we need to access the string's length, and possibly split the string first.

Example

To begin we introduce a 5-byte string containing the word "bird" and a period. This is the data we run our loops on. We loop over the string in 2 different ways.

Version 1 For the first version, we use a for-loop. We must access the length of the string with strlen() first.

Version 2 Here we use a foreach-loop over the string. We convert the string into an array with str_split, and then foreach will work.

Important We access the bytes from the string with strlen and the indexing operation. For multi-byte characters, we need a different function.

$value = "bird.";

// Version 1: get string length, then loop over string.
$len = strlen($value);
echo "Strlen = {$len}\n";

// Loop over the string indexes and access each char.
for ($i = 0; $i < $len; $i++) {
    $c = $value[$i];
    echo "Char = " . $c . "\n";
}

// Version 2: separate the string into letters, and loop over each letter.
$chars = str_split($value);
foreach ($chars as $c) {
    echo "Foreach char = {$c}\n";
}Strlen = 5
Char = b
Char = i
Char = r
Char = d
Char = .
Foreach char = b
Foreach char = i
Foreach char = r
Foreach char = d
Foreach char = .

Looping over, and testing, individual bytes (or chars) from a string is often required. In ASCII strings, bytes are the same thing as chars.

Often when we need to access the individual bytes from a string, it is useful to simply convert the string to an array. This can be done with str_split().