Best Practices for Using finfo::set_flags with finfo_file()—Do You Know Them?

gitbox 2025-09-12

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<p></span><?php<br>
<span class="hljs-comment">/**</p>
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<p>Title: Best Practices for Using finfo::set_flags with finfo_file()—Do You Know Them?</p>
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<p>In PHP, the finfo class offers an efficient and reliable way to handle file type detection.</p>
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<p>The combination of finfo::set_flags() and finfo_file() allows for more precise and flexible file type checking.</p>
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<p>finfo::set_flags() Function</p>
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<p>finfo::set_flags() is used to set flag values in the finfo object while performing file information checks.</p>
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<p>These flags control the detail and handling of the returned result, such as:</p>
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<p>FILEINFO_MIME_TYPE: Returns only the MIME type.</p>
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<p>FILEINFO_MIME: Returns complete MIME information, including charset.</p>
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<p>FILEINFO_PRESERVE_ATIME: Does not modify the access time when checking files.</p>
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<p>FILEINFO_RAW: Returns raw information without parsing.</p>
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<p>By setting appropriate flags, different requirements can be met for various scenarios.</p>
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<p>finfo_file() Function</p>
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<p>finfo_file() is the core method used to detect the MIME type or other information of a specified file.</p>
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<p>The usage is as follows:</p>
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$finfo = new finfo();

$type = $finfo->file('example.jpg');

echo $type; // Output: image/jpeg

finfo_file() returns the corresponding file information based on the flags set in the finfo object.

Best Practices

Set Default Flags When Creating finfo Object

$finfo = new finfo(FILEINFO_MIME_TYPE);

This ensures that the returned value is always the MIME type, avoiding additional parsing later.

Dynamically Modify Flags When Necessary

$finfo->set_flags(FILEINFO_MIME | FILEINFO_PRESERVE_ATIME);

For temporary needs, you can dynamically adjust the flags after creating the object without re-instantiating it.

Use Exception Handling

try {

$finfo = new finfo(FILEINFO_MIME_TYPE);

$type = $finfo-&gt;file(&#039;example.jpg&#039;);

if ($type === false) {

    throw new Exception(&#039;Unable to identify file type&#039;);

echo "File type: $type\n";

} catch (Exception $e) {

echo &#039;Error: &#039; . $e-&gt;getMessage();

}

This ensures that the program can handle cases where the file is missing or has an abnormal format, without crashing.

Avoid Recreating the Object

If you need to check a large number of files, it’s recommended to reuse the same finfo object to improve performance:

$finfo = new finfo(FILEINFO_MIME_TYPE);

$files = ['a.jpg', 'b.png', 'c.gif'];

foreach ($files as $file) {

echo $finfo-&gt;file($file) . "\n";

}

Conclusion:

Using finfo::set_flags() allows for flexible file detection output.

finfo_file() is the core method for retrieving file types.

Default flag settings when creating objects + reuse of objects + exception handling = best practices.

With these methods, you can retrieve file information more efficiently and safely in PHP.
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finfo::set_flags