What’s the Difference Between PHP’s fpassthru and fread Functions? What Are Their Use Cases?

gitbox 2025-08-27

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What’s the Difference Between PHP’s fpassthru and fread Functions? What Are Their Use Cases?<br>
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<p>echo <span><span class="hljs-string">"<p>In PHP, <code>fpassthru()

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fpassthru() directly reads and outputs everything from the current file pointer position to the end of the file, until the file ends or an error occurs. This function sends the read content directly to the browser or standard output, instead of returning it as a string.

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Automatically outputs the read content, no need for manual echo.

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Suitable for directly sending file content to the client, such as displaying images, file downloads, etc.

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Faster reading speed and simpler code.

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2. fread()

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Function prototype:

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string fread ( resource $handle , int $length )

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fread() reads a specified length of content starting from the current file pointer position and returns it as a string. After reading, the content is not automatically output; the developer must handle output or further logic manually.

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Flexible, allows reading any part of the file as needed.

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Useful when you need to further process the content, such as parsing text or analyzing files.

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Requires manual output of the read content.

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3. Comparison of Use Cases

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fpassthru(): Best for direct file transmission scenarios, such as file downloads, image display, or video streaming, where the file content is sent directly to the client.

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fread(): Best for scenarios where the file content needs to be processed, such as parsing text, reading large files in chunks, or extracting specific information.

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4. Example Code

echo "Using fpassthru() to output an entire file:
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<br>
$fp = fopen('example.txt', 'rb');<br>
if ($fp) {<br>
fpassthru($fp);<br>
fclose($fp);<br>
}<br>

echo "Using fread() to read and process file content:
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echo "

<br>
$fp = fopen('example.txt', 'rb');<br>
if ($fp) {<br>
while (!feof($fp)) {<br>
$chunk = fread($fp, 1024); // Read 1024 bytes at a time<br>
// Process the content read<br>
echo strtoupper($chunk);<br>
}<br>
fclose($fp);<br>
}<br>

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Summary

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In summary, fpassthru() is better suited for “read and output” scenarios, simple and efficient; while fread() is more flexible, ideal for complex applications that require processing of file content. Which function to use depends on your specific needs.

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