PHP - String

Character Indexing

A string can be seen as an array of characters and can be accessed and modified by specifying the zero-based offset

// Get the first character of a string
$str = 'This is a test.';
$first = $str[0];

// Get the third character of a string
$third = $str[2];

// Modify the third character of a string
$str[3] = 'e';

Length

strlen($str)

All String functions

String functions

Replace

• Exact: Suppressing a / str_replace

$lastPart = str_replace("/", "", $lastPart);

• Regexp: preg_replace. Example: <code babel by <code javascript

$matchedTextToRender = preg_replace('/<code[\s]+babel/', '<code javascript', $match);

Split

• preg_split: Count the number of line an HTML document by splitting by the p, h, br,tr,li element

$localCount = count(preg_split("/<\/p>|<\/h[1-9]{1}>|<br|<\/tr>|<\/li>/",$section['content']));

• split (deprecated in favor of preg_split)

Contains

• str_contains (from php 8)

if (str_contains('abc', '')) {
    echo "Checking the existence of the empty string will always return true";
}

• strpos for an exact match

$mystring = 'abc';
$findme   = 'a';
$pos = strpos($mystring, $findme);

// Note our use of ===.  Simply == would not work as expected
// because the position of 'a' was the 0th (first) character.
if ($pos === false) {
    echo "The string '$findme' was not found in the string '$mystring'";
} else {
    echo "The string '$findme' was found in the string '$mystring'";
    echo " and exists at position $pos";
}

• preg_match

# contains date, created or modified
preg_match('/date|created|modified/i', $value)

Extract

preg_match captures groups and returns them into the $matches third parameter.

Start with

if (strpos($string, 'prefix') === 0) {
   // It starts with 'prefix'
}

End with

• php8: str_ends_with
• with strrpos

$haystack = 'light-gradient';
$suffix = '-gradient';
$suffixStartPosition = strlen($haystack) - strlen($suffix );
if (strrpos($haystack, $suffix ) === $suffixStartPosition){
    $mainColorValue = substr($haystack ,0,$suffixStartPosition);
    ....
}

• or last characters ie substr(“mystring”, -1)

substr($src, -4) === ".svg"

Last character

substr("mystring", -1);
mb_substr("mystring", -1);

Upper First Character

ucfirst("name")

First and last position

• strpos - first position of a character
• strrpos - last position of a character

Lowercase

The function is strtolower

• isLowercase test snippet.

if ($string === strtolower($string){
   echo "string is lowercase"
}

Uppercase

strtoupper

Repeat

str_repeat

echo str_repeat("-=", 10);

Contains

• strpos

if (strpos($haystack,$needle)!==false){
   // foo
} else {
  // bar
}

• preg_match
• From php 8.0, str_contains

Match

See preg_match

Loop through characters

• On Text - single-byte character set (SBCS)

for ($i = 0; $i < strlen($s); $i++) {
    $char = $s[$i]; 
    echo $char;
}

• On Text - Double Byte Character Set

for ($i = 0; $i < mb_strlen($s); $i++) {
    $char = mb_substr($s, $i, 1);
   echo $char;
}

A non-numeric value encountered

Be careful to not use the + sign to concatenate string. Use .

Offset not contained in string

You may encounter this message:

PHP Warning:  strpos(): Offset not contained in string

It means that the offset used in the strpos function is higher than the length of the string minus 1 (offset starts at 0)

Quick fix with a conditional

if ($offset < (strlen($string) - 1)) {
  $pos = strpos($string, $searchChar, $offset)
}