Why ob start used in php

This function will turn output buffering on. While output buffering is active no output is sent from the script other than headers , instead the output is stored in an internal buffer. Some web servers e. Apache change the working directory of a script when calling the callback function.

You can change it back by e. If multiple output callback functions are active, output is being filtered sequentially through each of them in nesting order. If output buffering is still active when the script ends, PHP outputs the contents automatically. This function takes a string as a parameter and should return a string. When callback is called, it will receive the contents of the output buffer as its parameter and is expected to return a new output buffer as a result, which will be sent to the browser.

If the callback is not a callable function, this function will return false. This is the callback signature:. If callback returns false original input is sent to the browser. The callback parameter may be bypassed by passing a null value. If you call them from callback function, the behavior is undefined.

If you would like to delete the contents of a buffer, return "" a null string from callback function. The default value 0 means that the output function will only be called when the output buffer is closed.

The flags parameter is a bitmask that controls the operations that can be performed on the output buffer. Returns true on success or false on failure. Example 1 User defined callback function example. Example 2 Creating an unerasable output buffer. Submit a Pull Request Report a Bug.

Warning Some web servers e. Parameters callback An optional callback function may be specified. Return Values Returns true on success or false on failure. Useful if you have a complex script that, for performance reasons, you do not want site visitors to run repeatedly on demand. Output Buffering even works in nested scopes or might be applied in recursive structures If you're using object-orientated code in PHP you may, like me, want to use a call-back function that is inside an object i.

So every time you do an echo, the output of that is added to the buffer. Trivial example: say you want to show the user an error message, but the script has already sent some HTML to the browser. It'll look ugly, with a half-rendered page and then an error message.

Here the output is a string that is mentioned with the help of the echo statement. Check out the output so that you will understand what is happening in the syntax. Here at first, inside of the PHP tags, a function called callback is created with the buffer1 as a parameter. Then the function parenthesis are closed. Then HTML tags are used. The string text can be a string or some paragraph that is actually mentioned based on our requirement. So to recognize this we used some string text with ECHO is used.

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