Question

根据PHP manual在定义之前调用用户定义的函数不会产生错误，除了：

当以条件方式定义函数时......必须在被调用之前处理它的定义。

示例：

input_shape

引发致命错误：

Traceback (most recent call last):
File "trajecgen_keras.py", line 131, in <module>
    tf.app.run()
File "/home/.../lib/python3.5/site-packages/tensorflow/python/platform/app.py", line 124, in run
    _sys.exit(main(argv))
File "trajecgen_keras.py", line 85, in main
    input_shape=train_data.shape))
File "/home/.../lib/python3.5/site-packages/keras/models.py", line 467, in add
    layer(x)
File "/home/.../lib/python3.5/site-packages/keras/engine/topology.py", line 619, in __call__
    output = self.call(inputs, **kwargs)
File "/home/.../lib/python3.5/site-packages/keras/layers/wrappers.py", line 211, in call
    y = self.layer.call(inputs, **kwargs)
File "/home/.../lib/python3.5/site-packages/keras/layers/convolutional.py", line 168, in call
    dilation_rate=self.dilation_rate)
File "/home/.../lib/python3.5/site-packages/keras/backend/tensorflow_backend.py", line 3335, in conv2d
    data_format=tf_data_format)
File "/home/.../lib/python3.5/site-packages/tensorflow/python/ops/nn_ops.py", line 753, in convolution
    name=name, data_format=data_format)
File "/home/.../lib/python3.5/site-packages/tensorflow/python/ops/nn_ops.py", line 799, in __init__
    input_channels_dim = input_shape[num_spatial_dims + 1]
File "/home/../lib/python3.5/site-packages/tensorflow/python/framework/tensor_shape.py", line 521, in __getitem__
    return self._dims[key]
IndexError: list index out of range

通过上面的解释，我想在下面的代码中产生相同的错误：

bar();
$makefoo = true;
if ($makefoo) {
    function bar() {
        echo "I don't exist.\n";
    }
}

但是it doesn't。在描述此行为的手册中我缺少什么？

Answer 1

foo();
bar();
function foo() {
    $makefoo = true;
    if ($makefoo) {
        function bar() {
            echo "I don't exist until foo() is called.\n";
        }
    }
}

PHP代码分两次执行：首先是解析和编译步骤，然后是运行时。像foo这样的普通函数可以在解析时定义;它们是无条件的，不依赖于运行时信息。

因此function foo是在解析时定义的，然后在运行时foo()被调用，这会创建function bar，因此您可以在之后立即调用bar()。

在定义之前调用嵌套的用户定义函数

1 个答案: