Basic php related functions

##1.join():

join() The function returns a string composed of array elements.

join() function is an alias of the implode() function.

join() The function accepts two parameter orders. However, due to historical reasons, explode() does not work. You must ensure that the separator parameter comes before the string parameter.

join() The separator parameter of the function is optional. However, for backward compatibility, it is recommended that you use two parameters.

join(separator,array)

separator:Optional,Specifies the content placed between array elements,The default is "" (empty string) or it can be "+","-"etc.

array:Required,An array to be combined into a string.

2.array_keys()

:

Function return A new array containing all the keys in the array. If the second parameter is provided, only the key name with the key value is returned.

For example:

<?php
$a=array("Volvo"=>"XC90","BMW"=>"X5","Toyota"=>"Highlander");
print_r(array_keys($a));
?>

Running result:

Array ( [0] => Volvo [1] => BMW [2] => Toyota )

：Definition and usage:

The function returns an array containing the given array Array of all key values, but no key names. Tip: The returned array will use numeric keys, starting at

and increasing by 1 . For example:

<?php
$a=array("Name"=>"Bill","Age"=>"60","Country"=>"USA");
print_r(array_values($a));
?>

Running result:

Array ( [0] => Bill [1] => 60 [2] => USA )

Function:

If there is a statement such as a query, it will return resources. To put it bluntly, it is the data result set you want to check; if there are statements such as additions, deletions, and modifications, it will return true or false. If you want to use this data result set, you must use

and other functions to obtain the data inside, which is mysql_query()Must be used in conjunction with the above functions.

will take out a row of records from the result set, and the resource pointer will jump down, In other words, when

is used again, a new row of records will be obtained,

以此类推，每执行一次mysql_fetch_assoc，取一新行，直到取出最后一行，

再取时，因为已经没有下一行，就会返回false。

综上所述：

在你的第一个例子中，

$s_as=mysql_fetch_assoc($s_re);
while($s_as)

是取出结果集的第一行，第一行不为空吧，所以$s_as不等于false，所以，当你用while($s_as)时，相当于while(true),是一个死循环,应该改成：

$s_as = mysql_fetch_assoc($s_re);
while($s_as) {
$arr[] = $s_as;
$s_as = mysql_fetch_assoc($s_re); //你没写这行，所以$s_as永远不是false造成死循环。
}

第二个例子中，则不同，while($s_as=mysql_fetch_assoc($s_re)),每次取一行，当取到最后一行时，再没有一下行了，mysql_fetch_assoc就会返回flash,也就是$s_as=false,while循环就会停止

6.substr(string,start,length):

处理字符串string。

start:规定再字符串的何处开始。

length：可选，规定被返回字符串的长度。默认是知道字符串的结尾。

7.foreach():

用于遍历操作或输出数组，foreach() 仅能用于遍历数组或对象，当试图将其用于其它数据类型或者一个未初始化的变量时会产生错误.

语法：

foreach (array as $value)
statement
// 或者：
foreach (array as $key => $value)
statement

上述语法中，每次循环将当前单元的值赋给 $value 并且数组内部的指针向前移一步。在第二种语法格式中还将当前单元的键名也会在每次循环中赋给变量 $key。

8.文件路径处理函数

basename():获取文件路径的文件名.

dirname():获取文件路径的目录

9.字符串处理函数

stripos(string,find,start)

定义和用法

stripos() 函数查找字符串在另一字符串中第一次出现的位置（不区分大小写）。

注释：stripos() 函数是不区分大小写的。

注释：该函数是二进制安全的

10.floor() Function :Round down to the nearest integer.

11.feof ( ) function:

##Function prototype: int feof(FILE * stream);

is located in the header file: stdio.h

Return value: Returning a non-zero value means that the end of the file has been reached

Function description:

12.fscanf()

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