PHP for loop Exercises: Using nested for loop, construct a specific pattern
PHP for loop: Exercise-4 with Solution
Create a script to construct the following pattern, using a nested for loop.
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Pictorial Presentation:

Sample Solution:
PHP Code:
<?php
$n=5;
for($i=1; $i<=$n; $i++)
{
for($j=1; $j<=$i; $j++)
{
echo ' * ';
}
echo '\n';
}
for($i=$n; $i>=1; $i--)
{
for($j=1; $j<=$i; $j++)
{
echo ' * ';
}
echo '\n ';
}
?>
Sample Output:
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Flowchart :

PHP Code Editor:
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Previous: Create a script to construct the specific pattern, using nested for loop.
Next: Write a program to calculate and print the factorial of a number using a for loop. The factorial of a number is the product of all integers up to and including that number, so the factorial of 4 is 4*3*2*1= 24.
What is the difficulty level of this exercise?
PHP: Tips of the Day
PHP - How do I implement a callback in PHP?
The manual uses the terms "callback" and "callable" interchangeably, however, "callback" traditionally refers to a string or array value that acts like a function pointer, referencing a function or class method for future invocation. This has allowed some elements of functional programming since PHP 4. The flavors are:
$cb1 = 'someGlobalFunction'; $cb2 = ['ClassName', 'someStaticMethod']; $cb3 = [$object, 'somePublicMethod']; // this syntax is callable since PHP 5.2.3 but a string containing it // cannot be called directly $cb2 = 'ClassName::someStaticMethod'; $cb2(); // fatal error // legacy syntax for PHP 4 $cb3 = array(&$object, 'somePublicMethod');
This is a safe way to use callable values in general:
if (is_callable($cb2)) { // Autoloading will be invoked to load the class "ClassName" if it's not // yet defined, and PHP will check that the class has a method // "someStaticMethod". Note that is_callable() will NOT verify that the // method can safely be executed in static context. $returnValue = call_user_func($cb2, $arg1, $arg2); }
Modern PHP versions allow the first three formats above to be invoked directly as $cb(). call_user_func and call_user_func_array support all the above.
Notes/Caveats:
- If the function/class is namespaced, the string must contain the fully-qualified name. E.g. ['Vendor\Package\Foo', 'method']
- call_user_func does not support passing non-objects by reference, so you can either use call_user_func_array or, in later PHP versions, save the callback to a var and use the direct syntax: $cb();
- Objects with an __invoke() method (including anonymous functions) fall under the category "callable" and can be used the same way, but I personally don't associate these with the legacy "callback" term.
- The legacy create_function() creates a global function and returns its name. It's a wrapper for eval() and anonymous functions should be used instead.
Ref : https://bit.ly/2Zmqil0
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