8 PHP array interview questions, PHP array test questions

PHP array questions found online, prepare to do it yourself and record it.

1. Write a function to create an array with a length of 10. The elements in the array are increasing odd numbers, and the first item is 1.
Copy code The code is as follows:

function arrsort($first,$length){

$arr = array();
for($i=$first;$i<=$length;$i ){

$arr[] = $i*2-1;
}
return $arr;
}

$arr1 = arrsort(1,10);
Print_r($arr1);

Output:
Copy code The code is as follows:
Array ( [0] => 1 [1] => 3 [2] => 5 [3] => 7 [4] => 9 [5] => 11 [6] => 13 [7] => 15 [8] => 17 [9] => 19 )

2. Create an array with a length of 10. The numbers in the array are increasing geometric numbers, the ratio is 3, and the first item is 1.
Copy code The code is as follows:

//$num is the ratio
Function arrsort($first,$length,$num){

$arr= array();
             for($i=$first;$i<=$length;$i){

                          //pow($num,$i-2); returns $num raised to the ($i-2) power
                     $arr[] = $num*pow($num,$i-2);
          }
            return $arr;

$arr1 = arrsort(1,10,3);

Print_r($arr1);

Output:

Copy code The code is as follows: Array ( [0] => 1 [1] => 3 [2] => 9 [3] => 27 [4] => 81 [5] => 243 [6] => 729 [7] => 2187 [8] => 6561 [9] => 19683 )

3. Find the subscript of the largest number in the array.
Copy code The code is as follows: function maxkey($arr){

$maxval = max($arr);

foreach($arr as $key=>$val){

If($maxval == $val){

$maxkey = $key;
}
}
Return $maxkey;
}

$arr = array(0,-1,-2,5,"b"=>15,3);

echo maxkey($arr);

Output:

Copy code The code is as follows: b

4. Create an array with a length of 10. The elements in the array satisfy the rules of the Fibonacci sequence.

(The Fibonacci sequence, also known as the golden section sequence, refers to such a sequence: 1, 1, 2, 3, 5, 8, 13, 21,... In mathematics, the Fibonacci sequence It is defined recursively as follows: F0=0, F1=1, Fn=F(n-1) F(n-2) (n>=2, n∈N*). In particular, the 0th item is 0, item 1 is the first 1)

Copy code The code is as follows:

function arrFibo($len){

$arr[0] = 0;

$arr[1] = 1;
for($i=2;$i<$len;$i ){

$arr[$i] = $arr[$i-1] $arr[$i-2];
}
Return $arr;
}

echo "

";</p>
<p>
print_r(arrFibo(10));<br>
echo "

Output:

Copy code The code is as follows: Array
(
[0] => 0
[1] => 1
[2] => 1
[3] => 2
[4] => 3
[5] => 5
[6] => 8
[7] => 13
[8] => 21
[9] => 34
)

5. Calculate the difference between the largest number and the smallest number in the array.

Two methods:

①max/min

Output:

Copy code The code is as follows: 102

②sort sorts the elements from small to large/rsort sorts the elements from large to small
Copy code The code is as follows:

function arrsub($arr){

sort($arr);
$min = $arr[0];

rsort($arr);
$max = $arr[0];

$sub = $max - $min;

return $sub;
}

$arr = array(-1,-2,100);

echo arrsub($arr);

Output:

102

6. Write a method to directly intercept the last 5 items of an array with a length of more than 10, and change the order into the first 5 items, such as {1,2,3,4,5,6,7,8,9 ,10} becomes {6,7,8,9,10,1,2,3,4,5}.

Idea: First cut the array to the corresponding length (array_slice), and then splice the two arrays (array_merge)
Copy code The code is as follows:

function arrsort($arr){

$num = count($arr);

if($num > 10){

//array_slice($arr, starting position, interception length, retained index (default is false))
$arr_firstpart = array_slice($arr,0,$num-5,true);
$arr_lastpart = array_slice($arr,($num-5),5,true);
}else{

echo "The array does not exceed 10 elements, please re-enter";
exit();
}

//Splicing
$arr_new = array_merge($arr_lastpart,$arr_firstpart);

return $arr_new;
}

$arr = array("a"=>1,2,3,8,9,6,"b"=>5,-1,"c"=>8,0,7);

echo "

";</p>
<p>print_r($arr);</p>
<p>echo "<br>= = = = = After splicing = = = = <br><br>";</p>
<p>print_r(arrsort($arr));</p>
<p>echo "

Output:
Copy code The code is as follows:
Array
(
[a] => 1
[0] => 2
[1] => 3
[2] => 8
[3] => 9
[4] => 6
[b] => 5
[5] => -1
[c] => 8
[6] => 0
[7] => 7
)

= = = = = After splicing = = = =
Copy code The code is as follows:
Array
(
[b] => 5
[0] => -1
[c] => 8
[1] => 0
[2] => 7
[a] => 1
[3] => 2
[4] => 3
[5] => 8
[6] => 9
[7] => 6
)

When the array does not meet the length of 10:
Copy code The code is as follows:
$arr = array("a"=>1,2,3);

Output:
Copy code The code is as follows:
Array
(
[a] => 1
[0] => 2
[1] => 3
)

= = = = = After splicing = = = =

The array does not exceed 10 elements, please re-enter

7. Concatenate the two arrays into a new array.

Method ① Use array_merge() function
Copy code The code is as follows:
array_merge($arr1,$arr2);

Method ② Use the array_merge_recursive() function to recursively append the array

( The array_merge_recursive() function, like the array_merge() function, merges the elements of one or more arrays. The values in one array are appended to the previous array. And returns the resulting array.

However, unlike array_merge(), when there are duplicate key names, the value will not be overwritten, but multiple values with the same key name will be recursively formed into an array. )
Copy code The code is as follows:

$arr = array("a"=>1,"b"=>2,3);
$arr2 = array("a"=>Dee,3,5);

$arr3 = array_merge($arr,$arr2);
$arr4 = array_merge_recursive($arr,$arr2);

echo "

";<br>
Print_r($arr3);</p>
<p> echo "<br> = = = = = <br><br>";</p>
<p> print_r($arr4);<br>
echo "

Output:
Copy code The code is as follows:
Array
(
[a] => Dee
[b] => 2
[0] => 3
[1] => 3
[2] => 5
)

= = = = =
Copy code The code is as follows:
Array
(
[a] => Array
(
[0] => 1
[1] => )

[b] => 2

[0] => 3
[1] => 3
[2] => 5
)

The value 1 with index "a" in the first output array is indexed over by the value Dee with index "a" in the second array.

Method ③
Copy code The code is as follows:

function arrsort($arr1,$arr2){

$arr_new = $arr1;

foreach($arr2 as $key=>$val){

$arr_new[] = $val;
}

return $arr_new;

}

$arr1 = array("a"=>1,"b"=>2,3);

$arr2 = array("a"=>Dee,"c"=>3,5);

echo "

";<p>
print_r(arrsort($arr1,$arr2));<br>
echo "

Output:

Copy code The code is as follows: Array
(
[a] => 1
[b] => 2
[0] => 3
[1] => Dee
[2] => 3
[3] => 5
)

If it is an indexed array and there is a duplicate index, the duplicate index in the second array will be modified to a new index.

8. Array reverse order (rsort function cannot be used, new array cannot be generated)

Using the array_reverse() function will create a new array, so it cannot be used.

Copy code The code is as follows:

$arr = array("a","b","c",1,10);

$i = "";//The subscript of the number to be replaced
$j = "";//Temporary variable
$k = "";//The subscript of the number to be replaced

$len = count($arr);

$half_len = floor($len/2);//Round down, the rounded value is the number of loops

for($i=0;$i<$half_len;$i ){

$j = $arr[$i];

//Judge the odd or even number of arrays
If($len%2!=0){ //Odd number

          $k = $half_len*2-$i;
}else{

           //Even number
          $k = $half_len*2-$i-1;
}

$arr[$i] = $arr[$k];

$arr[$k] = $j;
}

echo "