Computer Programming Tutorials

<?php $string = 'ab cd ab cd ab'; $string = ' '.$string; // because the while loop below won't run if we find the first match in position 0 $find = 'ab'; $find_length = strlen($find); $offset = 1; // from this index the search of $find will start // strpos function returns false when offset value equals to string length, but returns error for more than that while($find_position = strpos($string, $find, $offset)) {        echo '<b>'.$find.'</b> is found at '.$find_position.'<br/>';         $offset = $find_position + $find_length; } ?>

<?php $string = 'hello 0'; for($i = 0; @$string[$i] || @$string[$i] == '0'; $i++); /* $string[$i] echoes an error message when $i = 7 and  @ (error control operator) hides that error. When the error occurs $string[$i] = Null because $i is undefined index number. Second condition is used here to treat '0' as a true value */ echo $i; // outputs 7 ?>

<?php $x = 1; // here I defined global variable x, now $_GLOBALS['x' => 1] function my_function() {       echo $x; // outputs a notice that says 'Undefined variable: x', because php functions don't access global variables directly, but through reference        $x = 2; // here I defined local variable x        echo $x; // outputs 2        global $x; // Now the local variable x has got the reference of the global variable x that means 'globals $x' statement equals to $x = &$_GLOBALS['x']. If there was no global variable named x then a global variable named x would be created containing null as its value and the local variable x would have its reference as value.        echo $x; // outputs 1 } my_function(); ?>

<?php $animal = CAT; // outputs Notice: Use of undefined constant cat - assumed 'cat' echo $animal; // ouputs CAT define('CAT', '4 legs'); $animal = CAT; echo $animal; // outputs 4 legs /* conclusion: undefined constant name and unquoted string value will be converted into string automatically */ ?>

<?php $day = 'Saturday'; switch($day) {     case 'Saturday':     case 'Sunday':         echo 'It\'s a weekend';     break;         default:         echo 'Not a weekend';     break; } ?>

<?php $number = 27; switch(true) {     case ($number > 100):         echo 'Bigger than hundred';     break;        case ($number < 100):         echo 'Lower than hundred';     break;        default:         echo 'Equal to hundred';     break; } ?>

<?php if(12 == '12a1') // '12a1' will be converted into 12 {     echo 'True'; } else {     echo 'False'; } // outputs True if(12 == 'a121') // here 'a121' will be converted into 0, because of non-numerical character up front {     echo 'True'; } else {     echo 'False'; } // outputs False if(12.5 == '12.5a') // here '12.5a' will be converted into 12.5 {     echo 'True'; } else {     echo 'False'; } // outputs True ?>

<?php $string = 'abc'; echo $string; // outputs abc $string++; echo $string; // outputs abd $string++; echo $string; // outputs abe ++$string; echo $string; // outputs abf ++$string; echo $string; // outputs abg $string--; echo $string; // outputs abg $string--; echo $string; // outputs abg --$string; echo $string; // outputs abg --$string; echo $string; // outputs abg /* Decrement operator doesn't have any effect on string but increment operator increases the last character of the string. If we use increment operator when the last character of a string is Z or, z then the the last character will be A or, a respectively. */ ?>

<?php $x = 1; $x = ($x++) + 1; // This statement equals to $x = 1 + 1, here $x++ statement puts the value of $x in its place and then execute itself. After that, $x = ($x++) + 1 which means $x = 1 + 1 is executed. echo $x; // outputs 2 ?>

<?php if(0 == 'Cat') {     echo 1; } // outputs 1 if(0.1 > 'Cat') {     echo 1; } // outputs 1 # strings are converted into 0 when strings are compared (using '==' operator) with numeric values ?>