What are the vulnerabilities of commonly used functions in PHP?

The previous article introduced you to "How to upload files in PHP? What do we need to pay attention to? 》, this article continues to introduce to you what are the vulnerabilities of commonly used functions in PHP? It has certain reference value. Friends in need can refer to it. I hope it will be helpful to everyone.

Vulnerabilities in commonly used functions in PHP:

• extract variable coverage vulnerability

• extract function: Import variables from the array into the current symbol table. It can be found in some mvc frameworks

• Extract function definition: int extract(array,extract_ rules,prefix)

• extract0 The function will check whether each key name is a legal variable name and also checks whether it conflicts with an existing variable name in the symbol table. The handling of illegal and conflicting key names will be determined based on this parameter.

extract_rules :

• EXTR_ OVERWRITE - Default. If there is a conflict, existing variables are overwritten.

• EXTR_ SKIP - If there is a conflict, do not overwrite existing variables.

• EXTR_ PREFIX. SAME - If there is a conflict, add a prefix to the variable name.

• EXTR_ PREFIX. ALL - Give all variable names Prefix prefix.

• EXTR_ PREFIX. INVALID - Prefix only illegal or numeric variable names with prefix.

• ##EXTR_ IF. EXISTS - Overwrites the values ​​of variables with the same name only if they already exist in the current symbol table. Others are not processed.

• EXTR_PREFIX_IF _EXISTS - Only when a variable with the same name already exists in the current symbol table. Create a variable name with a prefix attached and nothing else will be processed.

• EXTR_REFS - Extract variables as references. The imported variable still references the value of the array parameter.

We use code as an example to demonstrate the impact of the extract function on the current coverage table:

We first create a file, for example, there is a name in the current coverage table, and then we Output this variable,

<?php
$name = &#39;好久不见&#39;;
echo $name;
?>

The code result is as follows:

Then we use the extract function, and then we define an array, which will overwrite the current coverage silently The variables in the table mean that the "Long Time No See" we just wrote will be overwritten. The code is as follows:

<?php
$name = &#39;好久不见&#39;;
extract(array(&#39;name&#39;=>&#39;再见&#39;));
echo $name;
?>

The code result is as follows:

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