How to Use the Command 'phpcpd' (with Examples)

PhpCpd is a tool designed to detect duplicated code in PHP projects. Duplication in code can be costly in terms of maintenance and readability. This command-line utility aims to ease code refactoring by identifying instances of copy-pasted code within a codebase, highlighting areas for potential improvement and optimization. The tool’s robust detection capabilities even allow for fuzzy matching and customized search parameters, providing flexibility and accuracy in addressing code redundancy.

Use Case 1: Analyze Duplicated Code for a Specific File or Directory

Code:

phpcpd path/to/file_or_directory

Motivation:

Understanding code duplication within a specific file or directory is crucial for maintaining clean and efficient code. By using this command, developers can specifically target and assess a particular section of their codebase, making it easier to manage and refactor.

Explanation:

• phpcpd: This is the command to invoke the PHP Copy-Paste Detector tool.
• path/to/file_or_directory: This is the path to the file or directory you want to analyze. It can be an absolute path or a relative path from your current working directory.

Example Output:

Found 2 clones with 60 duplicated lines in 2 files:

  - <file1.php>: Lines 10-40
  - <file2.php>: Lines 50-80

Average size of duplication blocks is 30 lines

Use Case 2: Analyze Using Fuzzy Matching for Variable Names

Code:

phpcpd --fuzzy path/to/file_or_directory

Motivation:

Fuzzy matching helps in detecting similar code segments that may have slightly varying variable names. This can be particularly helpful in identifying cases where code is copied but variable names are changed to bypass exact matching detection.

Explanation:

• --fuzzy: This option enables fuzzy matching, allowing the tool to overlook minor differences like variable or parameter names.
• path/to/file_or_directory: The targeted location for code duplication assessment.

Example Output:

Found 3 clones with 50 duplicated lines in 2 files (fuzzy matching):

  - <file1.php>: Lines 10-30
  - <file2.php>: Lines 60-80

Variable names have been ignored during comparison

Use Case 3: Specify a Minimum Number of Identical Lines

Code:

phpcpd --min-lines 10 path/to/file_or_directory

Motivation:

Setting a minimum number of identical lines helps in filtering out irrelevant matches and focusing on substantial pieces of duplicated code. This is crucial for larger projects where smaller duplications may not significantly impact maintainability or performance.

Explanation:

• --min-lines 10: This argument sets the minimum number of identical lines to be considered as a duplication. By default, this is 5, but here it is set to 10 to capture larger blocks.
• path/to/file_or_directory: Specifies where to look for code duplication.

Example Output:

No clones found with at least 10 identical lines.

Use Case 4: Specify a Minimum Number of Identical Tokens

Code:

phpcpd --min-tokens 100 path/to/file_or_directory

Motivation:

Using tokens rather than lines as a measurement for duplication provides a more granular level of analysis. It allows developers to specify a threshold based on code structure rather than physical line count, making it more adaptable to a variety of coding styles.

Explanation:

• --min-tokens 100: This sets the minimum number of identical tokens required to report a duplication. By default, this is 70, aiming to detect more substantial similarities.
• path/to/file_or_directory: The file or directory to be analyzed.

Example Output:

Found 1 clone with 110 duplicated tokens in 1 file:

  - <file1.php>: Tokens 100-210

Use Case 5: Exclude a Directory from Analysis

Code:

phpcpd --exclude path/to/excluded_directory path/to/file_or_directory

Motivation:

Excluding specific directories is beneficial when certain parts of the codebase do not require analysis, such as libraries, third-party plugins, or pre-generated files. This enables focused analysis and optimizes processing time.

Explanation:

• --exclude path/to/excluded_directory: This option excludes a specified directory from the analysis. The path must be relative to the source directory specified.
• path/to/file_or_directory: The directory or file intended for the main analysis.

Example Output:

Excluding directory: path/to/excluded_directory
411/500 lines analyzed - Found no duplication.

Use Case 6: Output the Results to a PHP-CPD XML File

Code:

phpcpd --log-pmd path/to/log_file.xml path/to/file_or_directory

Motivation:

Outputting results to an XML file is particularly useful for later analysis, documentation, or integration into continuous integration and deployment pipelines. This format also facilitates further automated processing or sharing of the report with team members.

Explanation:

• --log-pmd path/to/log_file.xml: This argument specifies the path to save the log file in XML format, which follows a standard compatible with many other tools.
• path/to/file_or_directory: The source file or directory to analyze for code duplication.

Example Output:

An XML file will be created at the specified path containing the results of the duplication analysis, formatted as follows:

<?xml version="1.0"?>
<pmd-cpd>
    <duplication lines="60" tokens="300">
        <file path="<file1.php>" lines="10-40"/>
        <file path="<file2.php>" lines="50-80"/>
    </duplication>
</pmd-cpd>

Conclusion:

The ‘phpcpd’ command is an invaluable tool for PHP developers aiming to maintain high code quality by detecting and refactoring duplicated segments. By using options like fuzzy matching, setting minimum thresholds for lines or tokens, and selecting specific directories for analysis or exclusion, developers can tailor the tool’s functionality to suit their project’s needs, making the process of identifying and eliminating redundancy both efficient and effective.