if true false

some thing practical



<?php
define('val___nul', "");
define('val___nul5', "fillup feild!_please");

?>





<?php 

$a=val___nul!=val___nul5;
if($a=== true){ echo val___nul5;}
else {echo "its not ok";}

?>

<br>
First, you specify the operator <<<, followed by an IDENTIFIER, and then a newline. Next, you put a string value. Finally, you use the same

IDENTIFIER to close the string.

The following example defines a string using heredoc syntax:
<?php

$s = <<<EOT
I'm a string that is using
heredoc syntax. I can contain
single quotation marks (') and double quotation 
mark(") without using escape character
EOT;

echo $s;?>

Notice that PHP replaces the variables by their values in a string defined using heredoc syntax.

The nowdoc syntax is similar to the heredoc syntax except the identifier in nowdoc syntax is enclosed in single quotation marks.
<?php

$s = <<<'EOT'
I'm a string that is using
nowdoc syntax. I can contain
single quotation marks (') and double quotation 
mark(") without using escape character
EOT;

echo $s;?>


In addition, PHP does not parse and replace variables by their values in a string defined using nowdoc syntax.

Accessing characters in a string
To access a character of a string at a particular position, you use the following syntax:


$s[index]

<br>


<?php

$str = 'this is a PHP string';
$str[0] = 'T';

echo $str;?>


<br>
Getting the length of a string
To get the number of characters in a string, you use a built-in function strlen(). It accepts a string as a parameter and returns the number of

characters in that string. Let’s take a look a the following example of using the strlen() function:


<?php

$str = 'this is a PHP string';
echo strlen($str);?>
<br>

If you want to count the number of words in a string, you use the str_word_count() function instead.
<br>


<?php
$str = 'this is a PHP string';
echo str_word_count($str);
 // 5
?>

<br>

Comparing strings
PHP provides two built-in functions strcmp() and strcasecmp() that allow you to compare two strings. Both functions accept two string arguments and

return an integer number:

If two strings are equal, it returns 0.
If the first string is greater than the second string it returns a number that is greater than 0 .
If the first string is less than the second string, it returns a number that is less than 0.
The only difference between strcmp() and strcasecmp() functions is that the strcasecmp() function compares strings in case-insensitive manner

whereas the strcmp() function does not.

<br>


<?php 
$str1 = 'PHP String';
$str2 = 'php string';
$result = strcasecmp($str1,$str2);

if($result == 0){

 echo '$str1 and $str2 are equal';

}else if($result > 0){

 echo '$str1 is greater than $str2';

}else{
 echo '$str1 is less than $str2';
}?>


<br>

If you replace the strcasecmp() function by strcmp() function in the code snippet above, the output will be different.

Concatenating strings
PHP allows you to concatenate strings using period ( .) operator. If you concatenate a string with a variable that is not a string type, the result

is a string because PHP automatically converts the non-string variable into a string variable before concatenating.

The following example demonstrates strings concatenation:

<br>
<?php
   $str = 'This is' . ' a string';
   echo $str . '<br/>';

   $age   = 22;
   $s1 = 'years old';

   $s2 = 'Are you ' . $age . ' ' . $s1 . '?';
   echo $s2;
?>


<br>