How to use file_put_contents function in PHP
This time I will show you how to use the file_put_contents function in PHP. What are the precautions when using the file_put_contents function in PHP? Here are practical cases, let’s take a look.
Recently, I encountered a question on File Upload on EIS. I found that filtering < basically made many gestures invalid. I thought about it for a long time but didn’t solve this question. After the game, I found out that I was using arrays to solve the problem. However, the principle is analyzed here. Not much to say, let’s take a look at the detailed introduction.
Let’s take a look at the official website definition of the second parameter data of the file_put_contents function:
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As you can see, the data parameter can be an array, which will be automatically join('',$array)
converted into a string
When this function accesses files, it follows the following rules:
If FILE_USE_INCLUDE_PATH is set, then the built-in path for a copy of *filename* will be checked
- If the file does not exist, a file will be created
- Open the file
- If LOCK_EX is set, the file will be locked
- If FILE_APPEND is set, it will be moved to the end of the file. Otherwise, the contents of the file will be cleared
- Write data to the file
- Close the file and unlock all files
- If successful, this function returns the number of characters written to the file. On failure, False is returned.
But our string filtering function generally uses the preg_match function to filter, such as:
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We know that many functions that process strings will return NULL if an array is passed in, such as strcmp, strlen, md5, etc. But the preg_match function returns false if an error occurs. Here we can pass var_dump(preg_match('/</' ,$data));
To verify, in this case, the regular filtering of preg_match will be invalid
Therefore, I guess the file upload code is written like this
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I believe you have mastered the method after reading the case in this article. More exciting Please pay attention to other related articles on php Chinese website!
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The above is the detailed content of How to use file_put_contents function in PHP. For more information, please follow other related articles on the PHP Chinese website!

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