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PHP Exercises: Create a new string of the first half of a given string of even length

PHP Basic Algorithm: Exercise-63 with Solution

Write a PHP program to create a new string of the first half of a given string of even length.

Sample Solution:

PHP Code :

<?php
function test($s1)
{
   return substr($s1, 0, strlen($s1) / 2);
}

echo test("Hello")."\n";
echo test("Hi")."\n";

Sample Output:

He
H

Flowchart:

Flowchart: Create a new string of the first half of a given string of even length.

PHP Code Editor:

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Previous: Write a PHP program to create a new string using first two characters of a given string. If the string length is less than 2 then return the original string.
Next: Write a PHP program to create a new string without the first and last character of a given string of length atleast two.

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PHP: Tips of the Day

$GLOBALS: An associative array containing references to all variables which are currently defined in the global scope of the script. The variable names are the keys of the array

Example:

<?php
$myGlobal = "global"; // declare variable outside of scope
function test()
{
$myLocal = "local"; // declare variable inside of scope
 // both variables are printed
 var_dump($myLocal);
 var_dump($GLOBALS["myGlobal"]);
}
test(); // run function
// only $myGlobal is printed since $myLocal is not globally scoped
 
var_dump($myLocal);
var_dump($myGlobal); 
?>

Output:

string(5) "local"
string(6) "global"
NULL
string(6) "global"

In the above example $myLocal is not displayed the second time because it is declared inside the test() function and then destroyed after the function is closed.

Becoming global

To remedy this there are two options.

Option one: global keyword

function test()
{
 global $myLocal;
 $myLocal = "local";
 var_dump($myLocal);
 var_dump($GLOBALS["myGlobal"]);
}

The global keyword is a prefix on a variable that forces it to be part of the global scope.

Note that you cannot assign a value to a variable in the same statement as the global keyword. Hence, why I had to assign a value underneath. (It is possible if you remove new lines and spaces but I don't think it is neat. global $myLocal; $myLocal = "local").

Option two: $GLOBALS array

function test()
{
 $GLOBALS["myLocal"] = "local";
 $myLocal = $GLOBALS["myLocal"];
 var_dump($myLocal);
 var_dump($GLOBALS["myGlobal"]);
}

In this example I reassigned $myLocal the value of $GLOBAL["myLocal"] since I find it easier writing a variable name rather than the associative array.