How to use while to sum php arrays

Summing steps: 1. Define a variable assigned a value of 0 to store the summing result, with the syntax "$sum=0;"; 2. Use the while statement and each() and list() functions to traverse Array, syntax "while(list($key,$val)=each($arr)) {//Loop body statement block;}"; 3. In the loop body, use the "=" operator to change the array elements one by one Addition and summation, the syntax is "$sum =$val;", after the loop ends, the value of "$sum" is the summation result.

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

The while loop statement is a when loop statement , first judge the loop condition. When the condition is satisfied, the loop body will be executed. If it is not satisfied, it will stop.

while(表达式){    //表达式为循环条件
    PHP语句块;  //PHP语句块为循环体
}

Statement analysis:

• First calculate the value of "expression". When the value is true, execute the "PHP statement block" in the loop body;

  Note: The calculation result of "expression" is of Boolean type (TRUE or FALSE). If it is a value of other types, it will be automatically converted to a Boolean type value (because PHP is a weak language type and will be converted based on The value of the variable, automatically converting the variable to the correct data type).
  

  "Statement block" is a collection of one or more statements surrounded by { }; if there is only one statement in the statement block, you can also omit { }.
  

• After the execution is completed, return to the expression and calculate the value of the expression again for judgment. When the expression value is true, continue to execute the "statement block" ...This process will be repeated

• until the value of the expression is false before jumping out of the loop and executing the statement below while.

In PHP, the while statement can be used with the each() and list() functions to traverse the array and sum it.

• #each() function returns the current key value in the array and moves the array pointer forward. After each() is executed, the array pointer will stay at the next element in the array or at the last element when the end of the array is reached.

• The list() function is used to assign values ​​to a set of variables in one operation.

Implementation steps:

Step 1: Define a The variable is assigned a value of 0, which is used to store the summation result

$sum=0;

Step 2: Use the while loop each() function list() function to traverse the array

while( list($key, $val) = each($arr) ) {
	//循环体语句块;
}

Step 3: In the loop body, use the "=" operator to add and sum the array elements one by one

$sum+=$val;

After the loop ends, the value of $sum is the summation result.

Implementation example:

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);   
$arr = [1,2,3,4,5,6,7,8,9,10];
var_dump($arr);
$sum=0;
while( list($key, $val) = each($arr) ) {
	$sum+=$val;
}
echo "数组偶数和为：".$sum;
?>

##Description:

each() function

each() function returns the key name and key value of the current element and moves the internal pointer backward.

Tips: The each() function is deprecated in PHP 7.2.0.

The key name and key value of the element are returned to an array with four elements. Two elements (1 and Value) contain the key value, and two elements (0 and Key) contain the key name.

each(array)

Return value: Return the key name and key value of the current element. The element's key name and value are returned in an array with four elements. Two elements (1 and Value) contain the key value, and two elements (0 and Key) contain the key name. If there are no more array elements, the function returns FALSE.

list() function

list() function is used to assign values ​​to a set of variables in one operation.

list(var1,var2...)

ParametersDescriptionRequired . The first variable to be assigned a value. Optional. More variables need to be assigned values.

var1
var2,...

Return value: Returns the assigned array.

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