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Nested output buffers

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You can nest output buffers and fetch the level for them to provide different content using the ob_get_level() function. 

<?php

$i = 1;
$output = null;

while( $i <= 5 ) {
    // Each loop, creates a new output buffering `level`
    ob_start();
    print "Current nest level: ". ob_get_level() . "\n";
    $i++;
}

// We're at level 5 now
print 'Ended up at level: ' . ob_get_level() . PHP_EOL;

// Get clean will `pop` the contents of the top most level (5)
$output .= ob_get_clean();
print $output;

print 'Popped level 5, so we now start from 4' . PHP_EOL;

// We're now at level 4 (we pop'ed off 5 above)

// For each level we went up, come back down and get the buffer
while( $i > 2 ) {
    print "Current nest level: " . ob_get_level() . "\n";
    echo ob_get_clean();
    $i--;
}

Outputs: 

Current nest level: 1
Current nest level: 2
Current nest level: 3
Current nest level: 4
Current nest level: 5
Ended up at level: 5
Popped level 5, so we now start from 4
Current nest level: 4
Current nest level: 3
Current nest level: 2
Current nest level: 1
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Output buffering:
* Output Buffering
* Basic usage getting content between buffers and clearing
* Nested output buffers
* Running output buffer before any content
* Processing the buffer via a callback
* Using Output buffer to store contents in a file useful for reports invoices etc
* Stream output to client
* Capturing the output buffer to re-use later
* Typical usage and reasons for using ob start
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