PHP Buildpack v5.x Architecture Comparison

This document compares the PHP buildpack v5.x architecture with other Cloud Foundry buildpacks to demonstrate alignment with CF buildpack best practices.

Overview
Environment Variable Handling
Configuration Patterns
Service Binding Patterns
Profile.d Script Usage
Key Findings

Overview

The PHP buildpack v5.x has been refactored from Python (v4.x) to Go, aligning it with the architecture patterns used across all other Cloud Foundry buildpacks.

Buildpacks Analyzed

Buildpack	Language	VCAP_SERVICES Support	Config Pattern
PHP v5.x	Go	✅ Staging-time	Build-time placeholders
PHP v4.x	Python	✅ Staging + Runtime	Runtime rewrite
Go	Go	✅ Staging-time	No placeholders
Java	Go	✅ Staging-time	No placeholders
Ruby	Go	✅ Staging-time	No placeholders
Python	Go	✅ Staging-time	No placeholders
.NET Core	Go	✅ Staging-time	No placeholders
Node.js	Go	✅ Staging-time	No placeholders

Key Observation: All modern CF buildpacks (except PHP v4.x) use staging-time configuration with no runtime rewriting.

Environment Variable Handling

Pattern: Read During Staging, Configure at Build Time

All buildpacks follow this pattern:

STAGING PHASE:
1. Read environment variables (VCAP_SERVICES, VCAP_APPLICATION, etc.)
2. Parse and extract needed values
3. Write configuration files
4. Create profile.d scripts for runtime env vars

RUNTIME:
- Pre-configured files already in droplet
- profile.d scripts export additional env vars
- No config rewriting needed

PHP v5.x Implementation

Extension Context (supply phase):

// src/php/extensions/extension.go
func NewContext() (*Context, error) {
    // Read VCAP_SERVICES during staging
    if vcapServicesJSON := os.Getenv("VCAP_SERVICES"); vcapServicesJSON != "" {
        json.Unmarshal([]byte(vcapServicesJSON), &ctx.VcapServices)
    }
    
    // Read VCAP_APPLICATION during staging
    if vcapAppJSON := os.Getenv("VCAP_APPLICATION"); vcapAppJSON != "" {
        json.Unmarshal([]byte(vcapAppJSON), &ctx.VcapApplication)
    }
    
    return ctx, nil
}

Go Buildpack Implementation

AppDynamics Hook (supply phase):

// go-buildpack/src/go/hooks/appdynamics.go
func (h AppdynamicsHook) BeforeCompile(stager *libbuildpack.Stager) error {
    // Read VCAP_SERVICES during staging
    vcapServices := os.Getenv("VCAP_SERVICES")
    services := make(map[string][]Plan)
    json.Unmarshal([]byte(vcapServices), &services)
    
    if val, ok := services["appdynamics"]; ok {
        // Extract credentials
        appdEnv := map[string]string{
            "APPD_CONTROLLER_HOST": val[0].Credentials.ControllerHost,
            "APPD_ACCOUNT_KEY":     val[0].Credentials.AccountAccessKey,
        }
        
        // Write profile.d script
        stager.WriteProfileD("appdynamics.sh", scriptContents)
    }
}

Java Buildpack Implementation

VCAP Services Helper (supply phase):

// java-buildpack/src/java/common/context.go
type VCAPServices map[string][]VCAPService

func GetVCAPServices() (VCAPServices, error) {
    vcapServicesStr := os.Getenv("VCAP_SERVICES")
    if vcapServicesStr == "" {
        return VCAPServices{}, nil
    }
    
    var services VCAPServices
    err := json.Unmarshal([]byte(vcapServicesStr), &services)
    return services, err
}

Used in frameworks:

// java-buildpack/src/java/frameworks/sealights_agent.go
vcapServices, err := GetVCAPServices()
if sealightsService, found := findService(vcapServices, "sealights"); found {
    // Configure agent with service credentials
}

Configuration Patterns

What All Buildpacks Do

Pattern	PHP v5.x	Go	Java	Ruby	Python
Read env vars during staging	✅	✅	✅	✅	✅
Parse VCAP_SERVICES	✅	✅	✅	✅	✅
Write config files at build time	✅	✅	✅	✅	✅
Create profile.d scripts	✅	✅	✅	✅	✅
No runtime config rewriting	✅	✅	✅	✅	✅

What NO Buildpack Does (Except PHP v4.x)

Feature	PHP v4.x	All Others (including PHP v5.x)
Runtime config file rewriting	✅ Unique	❌ Never had
@{ARBITRARY_VAR} placeholders	✅ Unique	❌ Never had
Rewrite on every container start	✅ Unique	❌ Never had

Service Binding Patterns

Common Use Case: NewRelic Configuration

All buildpacks configure NewRelic the same way:

PHP v5.x

// src/php/extensions/newrelic/newrelic.go
const newrelicEnvScript = `if [[ -z "${NEWRELIC_LICENSE:-}" ]]; then
  export NEWRELIC_LICENSE=$(echo $VCAP_SERVICES | jq -r '.newrelic[0].credentials.licenseKey')
fi`

// Install() writes this script to profile.d during staging

Go Buildpack

// go-buildpack integrates NewRelic via multi-buildpack
// Same pattern: reads VCAP_SERVICES during staging

Java Buildpack

// java-buildpack reads VCAP_SERVICES during staging
// Configures NewRelic agent with extracted credentials

Common Use Case: Database Credentials

No buildpack writes database credentials to config files. All use application code:

PHP Application Code (Recommended)

<?php
$vcap = json_decode(getenv('VCAP_SERVICES'), true);
$db = $vcap['mysql'][0]['credentials'];

$pdo = new PDO(
    "mysql:host={$db['host']};dbname={$db['name']}",
    $db['username'],
    $db['password']
);
?>

Ruby Application Code

require 'json'

vcap_services = JSON.parse(ENV['VCAP_SERVICES'])
mysql = vcap_services['mysql'].first['credentials']

ActiveRecord::Base.establish_connection(
  adapter: 'mysql2',
  host: mysql['host'],
  username: mysql['username'],
  password: mysql['password'],
  database: mysql['name']
)

Java Application Code

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

String vcapServices = System.getenv("VCAP_SERVICES");
JsonNode services = new ObjectMapper().readTree(vcapServices);
JsonNode mysql = services.get("mysql").get(0).get("credentials");

String url = "jdbc:mysql://" + mysql.get("host").asText() + "/" + mysql.get("name").asText();
String username = mysql.get("username").asText();
String password = mysql.get("password").asText();

Pattern: All buildpacks expect applications to parse VCAP_SERVICES in code, not config files.

Profile.d Script Usage

Standard Pattern Across All Buildpacks

Purpose: Set environment variables at runtime based on staging-time analysis.

Location: deps/{idx}/profile.d/*.sh (sourced by Cloud Foundry at container startup)

PHP v5.x Examples

1. PHP Environment Setup

# Written by CreatePHPEnvironmentScript()
#!/usr/bin/env bash
: ${DEPS_DIR:=/home/vcap/deps}
export DEPS_DIR
export PATH="$DEPS_DIR/0/php/bin:$DEPS_DIR/0/php/sbin:$PATH"

2. NewRelic Extension

# Written by NewRelic extension during staging
#!/usr/bin/env bash
if [[ -z "${NEWRELIC_LICENSE:-}" ]]; then
  export NEWRELIC_LICENSE=$(echo $VCAP_SERVICES | jq -r '.newrelic[0].credentials.licenseKey')
fi

3. Extension Services (User Extensions)

# Generated from extension.json preprocess_commands
#!/usr/bin/env bash
# Extension environment variables
export MY_VAR='value'
export ANOTHER_VAR='value2'

Go Buildpack Examples

AppDynamics Configuration

# go-buildpack/src/go/hooks/appdynamics.go generates:
#!/usr/bin/env bash
export APPD_APP_NAME=my-app
export APPD_TIER_NAME=web-tier
export APPD_CONTROLLER_HOST=controller.example.com
export APPD_ACCOUNT_KEY=secret-key

Ruby Buildpack Examples

Rails SECRET_KEY_BASE

# ruby-buildpack generates during staging:
#!/usr/bin/env bash
export SECRET_KEY_BASE=${SECRET_KEY_BASE:-generated-secret-from-rake}
export RAILS_ENV=${RAILS_ENV:-production}

Key Observations

All buildpacks use profile.d for runtime environment setup
Scripts can parse VCAP_SERVICES at runtime if needed
Values extracted during staging can be baked into scripts
No buildpack rewrites config files at runtime

Key Findings

1. PHP v5.x is FULLY Aligned with CF Standards

The refactored PHP buildpack follows the exact same patterns as all other Cloud Foundry buildpacks:

Capability	Status
Read VCAP_SERVICES during staging	✅ Same as all buildpacks
Parse and use service credentials	✅ Same as all buildpacks
Write profile.d scripts	✅ Same as all buildpacks
No runtime config rewriting	✅ Same as all buildpacks
Build-time configuration	✅ Same as all buildpacks

2. The v4.x Runtime Rewrite Was PHP-Unique

The bin/rewrite script and @{ARBITRARY_VAR} placeholder support was:

❌ Not used by any other buildpack
❌ Not a CF buildpack standard
❌ Had performance/security trade-offs
✅ Removed for good reasons

3. All Migration Paths Exist

Every v4.x pattern has a v5.x equivalent that matches other buildpacks:

v4.x Pattern	v5.x Equivalent	Used By
Extension reads VCAP_SERVICES	Extension reads VCAP_SERVICES	All buildpacks
profile.d scripts	profile.d scripts	All buildpacks
App code parses VCAP_SERVICES	App code parses VCAP_SERVICES	All buildpacks
~~@{VCAP_SERVICES} in configs~~	❌ Never standard	PHP v4.x only

4. No Functionality Lost vs Other Buildpacks

When compared to other buildpacks (not v4.x), PHP v5.x has:

✅ Same capabilities
✅ Same patterns
✅ Same limitations
✅ Same extension model

The only "lost" feature is one that no other buildpack ever had.

Conclusion

PHP Buildpack v5.x Achieves Ecosystem Alignment

The migration from Python (v4.x) to Go (v5.x) successfully:

✅ Aligns with Cloud Foundry buildpack best practices
✅ Follows patterns used by Go, Java, Ruby, Python, .NET buildpacks
✅ Maintains all standard CF functionality
✅ Improves performance (no runtime rewriting)
✅ Enhances security (reduced runtime code execution)
✅ Increases maintainability (Go vs Python)

The v4.x Runtime Rewrite

While the removal of runtime config rewriting is a breaking change for PHP users:

It was never a CF standard (PHP-only feature)
It had performance and security costs
All use cases have standard CF equivalents
The change brings alignment with the broader ecosystem

Recommendation

The PHP buildpack v5.x should be considered fully compliant with Cloud Foundry buildpack architecture standards and best practices.

FilesExpand file tree

BUILDPACK_COMPARISON.md

Latest commit

History