xdebug

name: xdebug description: PHP debugging and analysis tools using Xdebug. Use when asked to trace, debug, profile, or analyze coverage of PHP code. Trigger phrases include "trace this function", "profile this code", "check coverage", "debug PHP", "set breakpoint", "find the bottleneck", "why is this slow", "トレース", "プロファイル", "カバレッジ".

Xdebug MCP Tools

Non-invasive PHP debugging and analysis tools. No var_dump() or code modification needed.

Tool Paths

Tools are installed globally via composer. Use absolute paths:

Tool Selection Guide

"Trace" Ambiguity

The word "trace" can mean different things:

• Forward Trace → xtrace (records execution from start to finish)
• Backtrace / Stack Trace → xback (shows call stack at a point)
• Step through / Debug → xstep (interactive with breakpoints)

xtrace - Forward Trace (Full)

Trace execution forward from start to finish. Captures complete execution flow, function calls, parameters, and timing data.

Output: JSON with $schema URL for semantic details and AI analysis strategies. Key fields: {lines, functions, max_depth, db_queries}

~/.composer/vendor/bin/xtrace [--json] [--context=TEXT] [--include-vendor=PATTERNS] -- command

Examples

~/.composer/vendor/bin/xtrace --context="Debug login" -- php login.php
~/.composer/vendor/bin/xtrace --context="Test analysis" -- vendor/bin/phpunit tests/UserTest.php
~/.composer/vendor/bin/xtrace --include-vendor="bear/*" -- php app.php

When to Use

• "Trace this code"
• "Show execution flow"
• "What functions are called?"
• General PHP debugging (default choice)

xstep - Forward Trace (Step-by-Step)

Stop at breakpoint, step forward N times, record variable changes at each step. See how variable values affect branching ("this variable was X, so it went into this branch").

Output: Slim, deduplicated JSON with a $schema URL — fields you might expect inline can live elsewhere, so read the linked schema to interpret the structure and reconstruct variable state. The schema is the source of truth; do not infer the format from examples.

~/.composer/vendor/bin/xstep --break=file.php:line --steps=N [--context=TEXT] [--include-vendor=PATTERNS] -- command

Options

• --break=file.php:line - Single breakpoint location
• --break=file.php:line:condition - Conditional (e.g., $user==null)
• --steps=N - Step forward N times from breakpoint
• --watch=EXPR - Only record steps when expression value changes (can specify multiple times)

Examples

# Step 20 times from line 42
~/.composer/vendor/bin/xstep --break="user.php:42" --steps=20 --context="Track auth" -- php user.php

# Conditional breakpoint
~/.composer/vendor/bin/xstep --break="user.php:15:\$id==null" --steps=10 -- php user.php

# Watch variable changes in loop
~/.composer/vendor/bin/xstep --break="loop.php:10" --watch="\$i" --steps=100 -- php loop.php

# Multiple watches
~/.composer/vendor/bin/xstep --break="app.php:25" --watch="\$user->getStatus()" --watch="count(\$items)" --steps=50 -- php app.php

Workflow Tips

• Need more steps? Set new breakpoint at where you stopped, run again
• Too much variable info? Use xtrace first to see flow, then xstep for details

When to Use

• "Track how variable changes step by step"
• "Why did it branch this way?"
• "What's the variable value at line X?"

xprofile - Performance Profiler

Identify performance bottlenecks with precision data.

Output: JSON with a schema URL. time_ms/memory_mb are measured from the cachegrind summary; bottlenecks is a structured array. Read the linked schema for the field shapes — don't infer the format here. Key fields: {time_ms, memory_mb, bottlenecks}

~/.composer/vendor/bin/xprofile [--json] [--context=TEXT] [--include-vendor=PATTERNS] -- command

Examples

~/.composer/vendor/bin/xprofile --context="Optimize processing" -- php process.php
~/.composer/vendor/bin/xprofile --json -- php script.php
~/.composer/vendor/bin/xprofile --include-vendor="doctrine/*" -- php app.php

When to Use

• "Profile this code"
• "Find bottlenecks"
• "Why is this slow?"
• "Memory usage analysis"

xcoverage - Code Coverage

Collect code coverage data for PHPUnit or any PHP script. Shows only uncovered lines (compact output).

Output: JSON with $schema URL for semantic details. Key fields: {summary: {coverage_percent, covered_lines, uncovered_lines}, uncovered: {file: [lines]}}

~/.composer/vendor/bin/xcoverage [--include-vendor=PATTERNS] -- command
~/.composer/vendor/bin/xcoverage -- vendor/bin/phpunit        # PHPUnit
~/.composer/vendor/bin/xcoverage -- php script.php            # Any PHP script

Examples

~/.composer/vendor/bin/xcoverage -- vendor/bin/phpunit
~/.composer/vendor/bin/xcoverage --include-vendor="bear/*,ray/di" -- vendor/bin/phpunit
~/.composer/vendor/bin/xcoverage -- vendor/bin/phpunit --filter testMethod

When to Use

• "Check test coverage"
• "Which lines are tested?"
• "Find untested code"

xback - Backtrace Capture

Get call stack (backtrace) at a specific line. Shows "who called this?" - the chain of function calls that led to this point.

Output: JSON with $schema URL for semantic details. Key fields: {backtrace: [{file, line, function, args}]}

~/.composer/vendor/bin/xback [--break=SPEC] [--depth=N] [--context=TEXT] -- command

Examples

~/.composer/vendor/bin/xback -- php script.php                    # First line
~/.composer/vendor/bin/xback --break=app.php:50 -- php app.php    # At breakpoint
~/.composer/vendor/bin/xback --depth=20 -- php main.php           # Deep trace

When to Use

• "Get backtrace at line X"
• "Show call stack"
• "How did execution reach this line?"

Common Options

Vendor Filtering

By default, vendor code is excluded to focus on your code. Use --include-vendor when needed:

--include-vendor="bear/*"           # Include specific framework
--include-vendor="bear/*,ray/di"    # Multiple packages
--include-vendor="*/*"              # Include all vendor (framework debugging)

JSON Schemas

• xtrace: https://koriym.github.io/xdebug-mcp/schemas/xtrace.json
• xstep: https://koriym.github.io/xdebug-mcp/schemas/xstep.json
• xprofile: https://koriym.github.io/xdebug-mcp/schemas/xprofile.json
• xcoverage: https://koriym.github.io/xdebug-mcp/schemas/xcoverage.json
• xback: https://koriym.github.io/xdebug-mcp/schemas/xback.json