How FFI::cdef() Parses C Declarations
The FFI::cdef() method in PHP plays a crucial role in allowing you to interact with native C libraries directly from your PHP code. Its primary function is to parse C declarations that you provide as a string, such as function signatures, struct definitions, and type declarations. When you call FFI::cdef(), PHP reads the C code you supply, checks it for correct C syntax, and constructs internal representations of the declared functions and types. This process allows PHP to expose those C functions and structures as callable objects or types within your PHP script at runtime.
For example, if you want to use a simple C function like int add(int, int), you must provide an accurate C declaration to FFI::cdef(). PHP then parses this declaration, creates a mapping between the PHP and C types, and enables you to call the function as if it were a native PHP method. Internally, PHP maintains metadata about the function's name, its argument types, and its return type, ensuring that calls from PHP are correctly marshaled to the underlying C implementation.
ffi_add_example.php
12345678910111213<?php // Declare and use a simple C function via FFI::cdef() // C declaration string for a simple add function $c_code = "int add(int a, int b);"; // Load the shared library (libadd.so must export 'add') $ffi = FFI::cdef($c_code, "libadd.so"); // Call the C function from PHP $result = $ffi->add(2, 3); echo "2 + 3 = " . $result . "\n";
A common mistake when using FFI::cdef() is failing to match the C declaration syntax exactly. For instance, forgetting a semicolon at the end of a declaration or specifying an incorrect type will cause PHP to throw a parse error. Always double-check your C declaration strings for proper syntax to avoid these issues.
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The FFI::cdef() method in PHP plays a crucial role in allowing you to interact with native C libraries directly from your PHP code. Its primary function is to parse C declarations that you provide as a string, such as function signatures, struct definitions, and type declarations. When you call FFI::cdef(), PHP reads the C code you supply, checks it for correct C syntax, and constructs internal representations of the declared functions and types. This process allows PHP to expose those C functions and structures as callable objects or types within your PHP script at runtime.
For example, if you want to use a simple C function like int add(int, int), you must provide an accurate C declaration to FFI::cdef(). PHP then parses this declaration, creates a mapping between the PHP and C types, and enables you to call the function as if it were a native PHP method. Internally, PHP maintains metadata about the function's name, its argument types, and its return type, ensuring that calls from PHP are correctly marshaled to the underlying C implementation.
ffi_add_example.php
12345678910111213<?php // Declare and use a simple C function via FFI::cdef() // C declaration string for a simple add function $c_code = "int add(int a, int b);"; // Load the shared library (libadd.so must export 'add') $ffi = FFI::cdef($c_code, "libadd.so"); // Call the C function from PHP $result = $ffi->add(2, 3); echo "2 + 3 = " . $result . "\n";
A common mistake when using FFI::cdef() is failing to match the C declaration syntax exactly. For instance, forgetting a semicolon at the end of a declaration or specifying an incorrect type will cause PHP to throw a parse error. Always double-check your C declaration strings for proper syntax to avoid these issues.
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