php how to use functions in string code example

Example: php string functions

#String Functions

substr()  #Returns a portion of a string
===========
<?php
    #substr()  Returns a portion of a string
    $output = substr('Hello', 1, 3);
    $output1 = substr('Hello', -2);//starts from the back of the string
    echo $output;
    echo '<br>';
    echo $output1;
?>
===============
strlen() #Returns the length of a string
===============
    $output = strlen('Hello');
    echo $output;
?>
===============
strpos() #finds the position of the first occurence of a sub string
===============
    $output = strpos('Hello World', 'o');
    echo $output;
    $output1 = strrpos('Hello World', 'o'); #last occurance
    echo $output1;
================
trim()  # trims white space
================
 $text = 'Hello World                ';
    var_dump($text);
    echo '<br>';
    $trimmed = trim($text);
    echo $trimmed;
    echo '<br>';
    var_dump($trimmed);
==================
strtoupper() # makes everything uppercase
==================
$text = 'Hello World';
    $uppercase = strtoupper($text);
    echo $uppercase;
==================
strtolower() #makes everything lowercase
==================
  $text = 'Hello World';
    $lowercase = strtolower($text);
    echo $lowercase;
==================
ucwords() #Capitalizes every word
===================
    $text = 'hello world';
    $proppercase = ucwords($text);
    echo $proppercase;
==================
str_replace() #Replace all occurances of a search string 
              #with a replacement
==================
$text = 'hello world';
    $wordreplace = str_replace('world', 'john', $text);
    echo $wordreplace;
=================
is_string() #Checks to see if it is a string
=================
    $val = 'Hello';
    $output = is_string($val);
    echo $output;
    echo '<br>';

    $values = array(true, false, null, 'abc', 33, '33',
    22.4, '22.4', '', ' ', 0, '0');

    foreach($values as $value){
        if(is_string($value)){
        echo "{$value} is a string<br>";
    }
}
=================
gzcompress() # Compress a string
=================
    $string = 
    "a;laksd;lk;lkasd;lkas;lk;lkd;lkasd;lka;lskd;lka;lkd;lk
    as;l;laksd;lk;lkasd;lkas;ldk;laskd;lakd;lkad;l
    adslkjlkasjdlkjlkjaslkjaslkdjlkajdlkajdlkajd
    alskdjlkasjdlkjadlkjadlkjadlkjadlajd
    adlkjlkjalksjdlkjlkjlkjklajsda";

    $compressed = gzcompress($string);
    
    echo $compressed;
    echo '<br>';

    $original = gzuncompress($compressed);

    echo $original;