PHP replace char with Unicode value inside string

<?php
$originalString = "Pritom K Mondal, 0154785";
function ord2($s2) {
    return "&#" . ord($s2) . ";";
}
echo preg_replace("/[^a-zA-Z0-9]/e", "ord2('\\0')", $originalString) ?>

And output will be as:

Pritom K Mondal, 0154785

Java - Replace all non digits with an empty character in a string

String cardNumber = "4444 3333 2222 111");
cardNumber = cardNumber.trim();
cardNumber = cardNumber.replaceAll("\\D+", "");

Output:
4444333322221111

php preg_replace

Example # Using backreferences followed by numeric literals

<?php
$string = 'April 15, 2003';$pattern = '/(\w+) (\d+), (\d+)/i';
$replacement = '${1}1,$3';
echo preg_replace($pattern, $replacement, $string);?>

The above example will output:

April1,200

Example # Using indexed arrays with preg_replace()

<?php
$string = 'The quick brown fox jumped over the lazy dog.'; 
$patterns = array(); 
$patterns[0] = '/quick/';
$patterns[1] = '/brown/'; 
$patterns[2] = '/fox/'; 
$replacements = array();
$replacements[2] = 'bear'; 
$replacements[1] = 'black'; 
$replacements[0] = 'slow';
echo preg_replace($patterns, $replacements, $string);?>

The above example will output:

The bear black slow jumped over the lazy dog.

Example # Strip whitespace

This example strips excess whitespace from a string.

<?php
$str = 'foo   o';$str = preg_replace('/\s\s+/', ' ', $str);// This will be 'foo o' nowecho $str;?>

Example # Using the count parameter

<?php
$count = 0;

echo preg_replace(array('/\d/', '/\s/'), '*', 'xp 4 to', -1 , $count);
echo $count; //3?>

The above example will output:

xp***to
3

If you would like to remove a tag along with the text inside it then use the following code. 

<?php 
preg_replace('/(<tag>.+?)+(<\/tag>)/i', '', $string); ?> 
example 
<?php $string='<span class="normalprice">55 PKR</span>'; ?> 
<?php 
$string = preg_replace('/(<span class="normalprice">.+?)+(<\/span>)/i', '', $string); ?> 
This will results a null or empty string. 

<?php 
$string='My String <span class="normalprice">55 PKR</span>'; 
$string = preg_replace('/(<span class="normalprice">.+?)+(<\/span>)/i', '', $string); ?>

PHP filter with preg_replace allow only letters and some other characters

Only receive - letters, numbers, spaces

$str = preg_replace("/[^A-Za-z0-9 ]/","",$str);
$str = preg_replace("/[^A-Za-z0-9\s]/","",$str);
$str = preg_replace("/[^A-Za-z0-9[:space:]]/","",$str);

$str = preg_replace("/([^a-z0-9A-Z[:space:]\'\"\?\!\,\.\-\:\~]+)/", "", $str]);

$str = preg_replace("/([--]+)/", "-", $str); 

$str = preg_replace("/<\/address>\r\n/e", "'</address>'", $str); 

When using the /e modifier in preg_replace, you have to pass a string of code to 

be evaluated as the replacement parameter, not an already-evaluated expression.

$str = preg_replace("/<\/address>[[:space:]]*?<address/e", "'</address><address'", $str);