PHP Mobile Internet Development Notes (4) - Custom Functions and Arrays_PHP Tutorial

1. Custom function

Custom functions are functions that we define ourselves. The format of custom functions in PHP is as follows:

function funname(arg1, arg2, arg3...){

//TODO

return values;

}

1. 	<?php  
       function fun($m, $n){  
           if($m==0 || $n==0){  
               return 0;  
           }else{  
               $a=$m*$n;  
               return $a;  
           }  
       }  
         
       $p=2;  
       $h=3;  
       echo $p."*".$h."=".fun($p,$h);  
   ?>  

Output result:

The following is another function with variable parameters

	<?php  
/* 
    function fun($m, $n){ 
        if($m==0 || $n==0){ 
            return 0; 
        }else{ 
            $a=$m*$n; 
            return $a; 
        } 
    } 
     
    $p=2; 
    $h=3; 
    echo $p."*".$h."=".fun($p,$h); */  
      
      
    function fun($m, $n=1, $x=2){  
        $a=$m*$n*$x;  
        return $a;  
    }  
      
    $p=2;  
    echo fun($p)."<br>";          // 2*1*2 = 4  
    echo fun($p, 3)."<br>";       // 2*3*2 = 12  
    echo fun($p, 3, 3)."<br>";    // 2*3*3 = 18  
?>  

Let’s take a look at custom function reference passing

	<?php  
    /*   
    function fun($m, $n){ 
        if($m==0 || $n==0){ 
            return 0; 
        }else{ 
            $a=$m*$n; 
            return $a; 
        } 
    } 
     
    $p=2; 
    $h=3; 
    echo $p."*".$h."=".fun($p,$h);  
    */  
      
    /* 
    function fun($m, $n=1, $x=2){ 
        $a=$m*$n*$x; 
        return $a; 
    } 
     
    $p=2; 
    echo fun($p)."<br>";          // 2*1*2 = 4 
    echo fun($p, 3)."<br>";       // 2*3*2 = 12 
    echo fun($p, 3, 3)."<br>";    // 2*3*3 = 18 
    */  
      
    function fun(&$n){  
        $n=$n*$n;  
    }  
    $p=2;  
    fun($p);  
    echo $p;  
?>  

2. Array definition and assignment

1. Basic writing format of array

Simple form: array(value1, value2, value3, ..........)

array("aa", 12, true, 2.2, "test", 50); //Get data through array subscript

Full form: array(key1=>value1, key2=>value2, ...)

array("title"=>"aa", "age"=>20); //Data can only be obtained by key name

2. How to create an array

	//第一种  
$arr1=array(11, 22, 33, "44");  
//第二种  
$arr2=array('a'=>'11', 'b'=>'22');  
//第三种  
$arr3[0]='20';  
$arr3[1]='30';  

3. Array operations

1. Modification

$arr=array(11, 22, 33, 44);

$arr[0]=55; //The array becomes $arr=array(55, 22, 33, 44);

2. Delete

$arr=array(11, 22, 33, 44);

unset($arr[0]); //The array becomes $arr=array(22, 33, 44);

3. Use

$arr=array(11, 22, 33, 44);

echo $arr[0];

$arr=array('a'=>11, 'b'=>22, 'c'=>33, 'd'=>44);

echo $arr['b']];

4. Traverse

$arr=array('a'=>11, 'b'=>22, 'c'=>33, 'd'=>44);

foreach($arr as $value){ //No key name

echo $value."
";

}

foreach($arr as $id=>$value){ //Output key and value

echo $id."__".$value."
";

}

4. Two-dimensional array

$arr=array(array("1","11","111"), array("2","22","222"));

echo $arr[1][2];

5. Array function

（1）array_change_key_case(array, case)

array: required, array.

case: optional, CASE_LOWER (default value, lowercase letters return the key of the array), CASE_UPPER (uppercase letters return the key of the array)

Function: Convert all KEYs in the array to uppercase or lowercase.

1. 	<?php  
       $a=array("a"=>"Cat","b"=>"Dog","c"=>"Horse");  
       print_r(array_change_key_case($a,CASE_UPPER));  
   ?>   
   结果：Array ( [A] => Cat [B] => Dog [C] => Horse )
   

(2)array_chunk(array,size,preserve_key)

array: required.

size: required, specifies how many elements each new array contains.

preserve_key: optional, true (preserve key name), false (new index)

Function: Divide an array into new array blocks.

	<?php  
    //array_chunk(array,size,preserve_key)  
      
    $a1=array("a"=>"Cat","b"=>"Dog","c"=>"Horse","d"=>"Cow");  
    print_r(array_chunk($a1,2));  
      
    $a2=array("a"=>"Cat","b"=>"Dog","c"=>"Horse","d"=>"Cow");  
    print_r(array_chunk($a2,2,true));  
      
?>   
结果：

Array ( [0] => Array ( [0] => Cat [1] => Dog ) [1] => Array ( [0] => Horse [1] => Cow ) )
Array ( [0] => Array ( [a] => Cat [b] => Dog ) [1] => Array ( [c] => Horse [d] => Cow ) )

......

There are many functions like this, you can check them when using them. The list is as follows (php represents the first version)

Function	Description	PHP
array()	Create an array.	3
array_change_key_case()	Returns an array whose keys are all uppercase or lowercase.	4
array_chunk()	Split an array into new array blocks.	4
array_combine()	Create a new array by merging two arrays.	5
array_count_values()	Used to count the number of occurrences of all values ​​in the array.	4
array_diff()	Returns the difference array of two arrays.	4
array_diff_assoc()	Compare the key name and key value, and return the difference array of the two arrays.	4
array_diff_key()	Compare key names and return the difference array of the two arrays.	5
array_diff_uassoc()	Calculate the difference set of arrays by doing index checking through the callback function provided by the user.	5
array_diff_ukey()	Use the callback function to compare the key names and calculate the difference set of the array.	5
array_fill()	Fills the array with the given values.	4
array_filter()	Use callback function to filter the elements in the array.	4
array_flip()	Swap the keys and values ​​in the array.	4
array_intersect()	Calculate the intersection of arrays.	4
array_intersect_assoc()	Compare the key name and key value and return the intersection array of the two arrays.	4
array_intersect_key()	Calculate the intersection of arrays using key name comparison.	5
array_intersect_uassoc()	Calculate the intersection of arrays with index checking, and use callback functions to compare the indices.	5
array_intersect_ukey()	Use callback function to compare key names to calculate the intersection of arrays.	5
array_key_exists()	Checks whether the given key or index exists in the array.	4
array_keys()	Returns all key names in the array.	4
array_map()	Apply the callback function to the cells of the given array.	4
array_merge()	Combine one or more arrays into one array.	4
array_merge_recursive()	Recursively merge one or more arrays.	4
array_multisort()	Sort multiple arrays or multidimensional arrays.	4
array_pad()	Pall the array to the specified length with values.	4
array_pop()	Pop the last element of the array (pop off the stack).	4
array_product()	Calculate the product of all values ​​in an array.	5
array_push()	Push one or more cells (elements) to the end of the array (push).	4
array_rand()	Randomly select one or more elements from the array and return it.	4
array_reduce()	Use a callback function to iteratively reduce the array to a single value.	4
array_reverse()	Reverse the order of elements in the original array, create a new array and return it.	4
array_search()	Search for the given value in the array and return the corresponding key name if successful.	4
array_shift()	Deletes the first element in the array and returns the value of the deleted element.	4
array_slice()	Retrieve a value from the array based on the condition and return it.	4
array_splice()	Remove part of the array and replace it with other values.	4
array_sum()	Calculate the sum of all values ​​in an array.	4
array_udiff()	Use callback function to compare data to calculate the difference of arrays.	5
array_udiff_assoc()	Calculate the difference set of arrays with index checking, and use callback functions to compare data.	5
array_udiff_uassoc()	With index check, calculate the difference set of the array, and use the callback function to compare the data and index.	5
array_uintersect()	Calculate the intersection of arrays and use callback functions to compare data.	5
array_uintersect_assoc()	Calculate the intersection of arrays with index checking and use callback functions to compare data.	5
array_uintersect_uassoc()	Calculate the intersection of arrays with index checking, and use callback functions to compare data and indexes.	5
array_unique()	Remove duplicate values ​​from the array.	4
array_unshift()	Insert one or more elements at the beginning of the array.	4
array_values()	Returns all values ​​in the array.	4
array_walk()	Apply a user function to each member of the array.	3
array_walk_recursive()	Apply the user function recursively to each member of the array.	5
arsort()	Reverse sort the array and maintain index relationship.	3
asort()	Sort the array and maintain index relationship.	3
compact()	Create an array including variable names and their values.	4
count()	Count the number of elements in an array or the number of attributes in an object.	3
current()	Returns the current element in the array.	3
each()	Returns the current key/value pair in the array and moves the array pointer forward one step.	3
end()	Point the internal pointer of the array to the last element.	3
extract()	Import variables from the array into the current symbol table.	3
in_array()	Checks whether the specified value exists in the array.	4
key()	Get the key name from the associative array.	3
krsort()	Sort the array in reverse order by key name.	3
ksort()	Sort the array by key name.	3
list()	Assign the values ​​in the array to some variables.	3
natcasesort()	Sort the array in a case-insensitive manner using the "natural sorting" algorithm.	4
natsort()	Sort the array using the "natural sorting" algorithm.	4
next()	Move the internal pointer in the array forward one position.	3
pos()	An alias for current().	3
prev()	Rewind the internal pointer of the array by one bit.	3
range()	Create an array containing elements in the specified range.	3
reset()	Point the internal pointer of the array to the first element.	3
rsort()	Sort the array in reverse order.	3
shuffle()	Rearrange the elements in the array in random order.	3
sizeof()	An alias for count().	3
sort()	Sort the array.	3
uasort()	Use user-defined comparison functions to sort values ​​in an array and maintain index association.	3
uksort()	Use user-defined comparison function to sort the keys in the array.	3
usort()	Sort the values ​​in an array using a user-defined comparison function.	3

http://www.bkjia.com/PHPjc/746360.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/746360.htmlTechArticle1. Custom functions Custom functions are functions that we define ourselves. The format of custom functions in PHP is as follows: function funname(arg1, arg2, arg3...){ //TODO return values; } ?...