PHP logical interview questions and answers

Dear Reader, in this article we are sharing PHP programming-related logical interview questions. Most of the interviewers will ask small PHP logical programs, So I have shared a few of the logical questions. If you want to ask or share any new questions write it in the comment section.

1.Sort an array without using any sorting function in PHP

1.a) Example $array = array(1, 6, 23, 10, 3, 2, 15,7); make this array ascending order without using any inbuilt function.

Answer :

<?php 
    $array = array(1, 6, 23, 10, 3, 2, 15,7);
    $total = count($array);
    for ($i=0; $i < $total; $i++) { 
        for ($j=$i+1; $j < $total; $j++) { 
            if($array[$i] > $array[$j]) {
                $temp = $array[$i];
                $array[$i] = $array[$j];
                $array[$j] = $temp;
            }
        }
    }
    echo '<pre>';
    echo "Ascending Sorted Array is: "; 
    print_r($array);
?>

OUTPUT

Before sorted Array is: Array
(
    [0] => 1
    [1] => 6
    [2] => 23
    [3] => 10
    [4] => 3
    [5] => 2
    [6] => 15
    [7] => 7
)
Ascending Sorted Array is: Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 6
    [4] => 7
    [5] => 10
    [6] => 15
    [7] => 23
)

1.b)Example $array = array(1, 6, 23, 10, 3, 2, 15,7); make this array descending order without using any inbuilt function.

<?php 
    $array = array(1, 6, 23, 10, 3, 2, 15,7);
    $total = count($array);
    for ($i=0; $i < $total; $i++) { 
        for ($j=$i+1; $j < $total; $j++) { 
            if($array[$i] < $array[$j]) {
                $temp = $array[$i];
                $array[$i] = $array[$j];
                $array[$j] = $temp;
            }
        }
    }
    echo '<pre>';
    echo "Descending Sorted Array is: "; 
    print_r($array);
?>

OUTPUT

Ascending Sorted Array is: Array
(
    [0] => 23
    [1] => 15
    [2] => 10
    [3] => 7
    [4] => 6
    [5] => 3
    [6] => 2
    [7] => 1
)

If you want to use PHP string build function for ascending just use sort().  PHP function for descending order rsort()

<?php 
    $array = array(1, 6, 23, 10, 3, 2, 15,7);
    $array2 = array(1, 6, 23, 10, 3, 2, 15,7);
    sort($array); // asending order
    rsort($array2); // descending order
    echo '<pre>'; print_r($array);
    echo '<pre>'; print_r($array2);
?>

2.Find the smallest and largest number in an array without using any function.

 a) Find the minimum array value $array = array(2,7,10,25,35,65,80);

<?php
    $array = array(2,7,10,25,35,65,80);
    $count = count($array);
    $min = $array[0];
    for ($i=0; $i < $count; $i++) { 
        if($array[$i] < $min)
        {
            $min = $array[$i];
        }
    }
    echo "minmum value $min";
    //output 2
?>

b) Find the maximum array value $array = array(2,7,10,25,35,65,80);

<?php
    $array = array(2,7,10,25,35,65,80);
    $count = count($array);
    $max = $array[0];
    for ($i=0; $i < $count; $i++) { 
        if($array[$i] > $max)
        {
            $max = $array[$i];
        }
    }
    echo "maximum value $max";
    //output 80
?>

With PHP function to find min min() and max max() array value.

<?php
    $array = array(2,7,10,25,35,65,80);
    $min = min($array);
    $max = max($array);
    //php function
?>

3.Write a program to make a chess:

<table width="300" cellspacing="0" cellpadding="0" border="1">  
<?php
for ($rows=1; $rows < 8 ; $rows++) { 
    echo '<tr>';
    for ($colum=1; $colum < 8; $colum++) { 
        $total = $rows + $colum;
        if($total % 2 ==0)
        {
            echo "<td width='40' height='40' bgcolor='#FFFFF'></td>";
        }
        else
        {
            echo "<td width='40' height='40' bgcolor='#00000'></td>";
        }
    }
    echo '</tr>';
 } 
?>
</table> 

OUTPUT

4.Find the email address

    a) $body = "This is a sentence and it has to find find@me.com in it"; 

    b) You are told that the variable $body has an email address but you are not told what is the email address or where it is in the text. Come up with two ways to find the email address. In the first use regular expressions. In the second don't use regular expressions.

Answer  A

$body = "This is a sentence and it has to find find@me.com in it"; 
echo $str = preg_replace('/([a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,6})/', '<a href="mailto:$1">$1</a>', $body);

Answer B

<?php
$body = "This is a sentence and it has to find find@me.com in it"; 
$email_find = explode(' ',$body);
foreach ($email_find as $key => $email) {
    if(filter_var($email, FILTER_VALIDATE_EMAIL)) {
        echo $email.'<br/>';
    }
}
?>

5.Find the prime numbers 1 to 100

Answer 

<?php
$number = 2;
while ($number < 100) 
{
    $divid_number=0;
    for ($i=1;$i<=$number;$i++) 
    { 
        if (($number%$i)==0) 
        {
            $divid_number++;
        }
    }
    if ($divid_number < 3) 
    {
        echo $number.'<br>';
    }
    $number = $number+1;
}
?>

OUTPUT

2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,

6.Remove duplicates from an array without using any inbuilt functions?

<?php
$number = array(1, 3, 4, 2, 1, 6, 4, 9, 7, 2, 9);
$newArr = array();
foreach($number as $val){
$newArr[$val] = $val;
}
echo '<pre>'; print_r($newArr);
?>

OUTPUT

Old Array
(
    [0] => 1
    [1] => 4
    [2] => 2
    [3] => 1
    [4] => 6
    [5] => 4
    [6] => 9
    [7] => 7
    [8] => 2
    [9] => 9
)
New Array
(
    [0] => 1
    [1] => 4
    [2] => 2
    [3] => 6
    [4] => 9
    [5] => 7
)

With PHP build function to remove the duplicate array

<?php
    $number = array_unique(array(1, 3, 4, 2, 1, 6, 4, 9, 7, 2, 9));
    echo '<pre>'; print_r($number);
?>

7.show only duplicate values from an array without built-in function PHP. ex array $arr = array(8,9,10,3,4,8,7,9,11,3);

Answer :

<?php
$arr = array(8,9,10,3,4,8,7,9,11,3);
foreach($arr as $key => $val)
{
  unset($arr[$key]); 
  if (in_array($val,$arr))
  {
    echo $val . ",";
  }
} // ouput 8,9,3
?>

8. Write a Function that combines two lists by alternatingly taking element. For example Given two lists [a, b, c] and [1, 2, 3] the function should return [a, 1, b, 2, c, 3]

Answer

<?php
    $arr = array(1,2,3);
    $arr1 = array(a,b,c);
    $new_array = array();

    for ($i=0; $i < count($arr); $i++)
    { 
        $new_array[] = $arr[$i];
        $new_array[] = $arr1[$i];

    }
    echo '<pre>'; print_r($new_array);
?>

OUTPUT

Array
(
    [0] => 1
    [1] => a
    [2] => 2
    [3] => b
    [4] => 3
    [5] => c
)

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