PHP study notes - PHP array summary

2), when $arr[ ] When assigning, the array subscript will be the current maximum subscript + 1 ($arr [max + 1]) as the subscript. Example:

 <?php
 $arr= array(1,'str',false);
 $arr[4]='4';
 $arr[]='x';
 $arr['int2']='7';
 $arr[]='xx';
 
 foreach($arr as $key=>$value)
 {
 echo $key.' ='.$value."<br>";
 }
 //output:
/*
0 =1
1 =str
2 =
4 =4
5 =x
int2 =7
6 =xx
*/
?>

4. Arrays in php will dynamically increase by themselves, which is different from c++. 5. Functions about arrays 1), count counts the number of arrays. 2), isarray determines whether a variable is an array 3), explode text segmentation. 4), unset destroys an element of a variable or array. The sequence of the array will not be changed after unset is destroyed. 6. Array operators $a+$b adds array b to array a, removing identical keys. Identical keys are not overwritten. The same goes for numerical subscripts

<?php
$a=array('a'=>'fsf','b'=>'fsdfss');
$b=array('a'=>'china','b'=>'huc','c'=>'lengai');
$c=$a+$b;
print_r($c);//Array ( [a] => fsf <strong> => fsdfss [c] => lengai )
?>

Code description: $a==$b The key values ​​of array a and array b are the same $a===$b Arrays a and b not only have the same key values, but the order must also be the same. $a$b array a and array b are different. $a!==$bArray a and array b are not congruent. Let’s summarize these, I hope it will be helpful to everyone. To learn PHP programming, come to Programmer’s Home.