我刚刚过这种问题。

检查 $配置的价值['从'] ['soap_url']制作API调用时。如果该值看起来像 http://example.com/api/soap?wsdl 那么你还在做，以V1的调用。更新它看起来像这样 http://example.com/api/v2_soap/?wsdl 。

I am trying to create a custom module that extends magento V2 soap calls. Most of my sources came from this post

How to setup custom api for Magento with SOAP V2?

This is the steps I've done to try to get it to work so far.

/app/etc/modules/Namespace_ImportExport.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Namespace_ImportExport>
            <active>true</active>
            <codePool>local</codePool>
            <depends>
                <Mage_Core />
            </depends>
        </Namespace_ImportExport>
    </modules>
</config>

/app/code/local/Namespace/ImportExport/etc/api.xml

<?xml version="1.0"?>
<config>
   <api>
     <resources>
       <importexport>
            <model>namespace_importexport/api</model>
            <title>api test</title>
            <methods>
                <foo translate="title" module="importexport">
                    <title>Foo Test</title>
                    <method>foo</method>
                </foo>
            </methods>
       </importexport>
    </resources>
    <v2>
        <resources_function_prefix>
           <importexport>importexport</importexport>
        </resources_function_prefix>
    </v2>
  </api>
</config>

/app/code/local/Namespace/ImportExport/etc/config.xml

<config>
    <modules>
        <Namespace_ImportExport>
            <version>0.0.1</version>
        </Namespace_ImportExport>
    </modules>
    <global>
        <models>
            <importexport><class>Namespace_ImportExport_Model</class></importexport>
        </models>
        <models>
            <catalog>
                <rewrite>
                    <product_api_v2>Namespace_ImportExport_Model_Product_Api_V2</product_api_v2>
                </rewrite>
            </catalog>
        </models>
    </global>
</config>

/app/code/local/Namespace/ImportExport/etc/wsdl.xml

Here I over wrote some existing modules declarations but you will find my custom module declarations at the bottom

<?xml version="1.0" encoding="UTF-8"?>
<definitions xmlns:typens="urn:{{var wsdl.name}}" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
    xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/" xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/" xmlns="http://schemas.xmlsoap.org/wsdl/"
    name="{{var wsdl.name}}" targetNamespace="urn:{{var wsdl.name}}">
    <types>
        <schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="urn:Magento">
            <import namespace="http://schemas.xmlsoap.org/soap/encoding/" schemaLocation="http://schemas.xmlsoap.org/soap/encoding/" />
            <complexType name="catalogProductCreateEntity">
                <all>
                    <element name="categories" type="typens:ArrayOfString" minOccurs="0" />
                    <element name="websites" type="typens:ArrayOfString" minOccurs="0" />
                    <element name="associated" type="typens:ArrayOfString" minOccurs="0" />
                    <element name="name" type="xsd:string" minOccurs="0" />
                    <element name="description" type="xsd:string" minOccurs="0" />
                    <element name="short_description" type="xsd:string" minOccurs="0" />
                    <element name="weight" type="xsd:string" minOccurs="0" />
                    <element name="status" type="xsd:string" minOccurs="0" />
                    <element name="url_key" type="xsd:string" minOccurs="0" />
                    <element name="url_path" type="xsd:string" minOccurs="0" />
                    <element name="visibility" type="xsd:string" minOccurs="0" />
                    <element name="category_ids" type="typens:ArrayOfString" minOccurs="0" />
                    <element name="website_ids" type="typens:ArrayOfString" minOccurs="0" />
                    <element name="has_options" type="xsd:string" minOccurs="0" />
                    <element name="gift_message_available" type="xsd:string" minOccurs="0" />
                    <element name="price" type="xsd:string" minOccurs="0" />
                    <element name="special_price" type="xsd:string" minOccurs="0" />
                    <element name="special_from_date" type="xsd:string" minOccurs="0" />
                    <element name="special_to_date" type="xsd:string" minOccurs="0" />
                    <element name="tax_class_id" type="xsd:string" minOccurs="0" />
                    <element name="tier_price" type="typens:ArrayOfString" minOccurs="0" />
                    <element name="meta_title" type="xsd:string" minOccurs="0" />
                    <element name="meta_keyword" type="xsd:string" minOccurs="0" />
                    <element name="meta_description" type="xsd:string" minOccurs="0" />
                    <element name="custom_design" type="xsd:string" minOccurs="0" />
                    <element name="custom_layout_update" type="xsd:string" minOccurs="0" />
                    <element name="options_container" type="xsd:string" minOccurs="0" />
                    <element name="additional_attributes" type="typens:associativeArray" minOccurs="0" />
                </all>
            </complexType>
            <complexType name="catalogProductReturnEntity">
                <all>
                    <element name="product_id" type="xsd:string" minOccurs="0" />
                    <element name="sku" type="xsd:string" minOccurs="0" />
                    <element name="set" type="xsd:string" minOccurs="0" />
                    <element name="type" type="xsd:string" minOccurs="0" />
                    <element name="categories" type="typens:ArrayOfString" minOccurs="0" />
                    <element name="websites" type="typens:ArrayOfString" minOccurs="0" />
                    <element name="associated" type="typens:ArrayOfString" minOccurs="0" />
                    <element name="created_at" type="xsd:string" minOccurs="0" />
                    <element name="updated_at" type="xsd:string" minOccurs="0" />
                    <element name="type_id" type="xsd:string" minOccurs="0" />
                    <element name="name" type="xsd:string" minOccurs="0" />
                    <element name="description" type="xsd:string" minOccurs="0" />
                    <element name="short_description" type="xsd:string" minOccurs="0" />
                    <element name="weight" type="xsd:string" minOccurs="0" />
                    <element name="status" type="xsd:string" minOccurs="0" />
                    <element name="url_key" type="xsd:string" minOccurs="0" />
                    <element name="url_path" type="xsd:string" minOccurs="0" />
                    <element name="visibility" type="xsd:string" minOccurs="0" />
                    <element name="category_ids" type="typens:ArrayOfString" minOccurs="0" />
                    <element name="website_ids" type="typens:ArrayOfString" minOccurs="0" />
                    <element name="has_options" type="xsd:string" minOccurs="0" />
                    <element name="gift_message_available" type="xsd:string" minOccurs="0" />
                    <element name="price" type="xsd:string" minOccurs="0" />
                    <element name="special_price" type="xsd:string" minOccurs="0" />
                    <element name="special_from_date" type="xsd:string" minOccurs="0" />
                    <element name="special_to_date" type="xsd:string" minOccurs="0" />
                    <element name="tax_class_id" type="xsd:string" minOccurs="0" />
                    <element name="tier_price" type="typens:ArrayOfString" minOccurs="0" />
                    <element name="meta_title" type="xsd:string" minOccurs="0" />
                    <element name="meta_keyword" type="xsd:string" minOccurs="0" />
                    <element name="meta_description" type="xsd:string" minOccurs="0" />
                    <element name="custom_design" type="xsd:string" minOccurs="0" />
                    <element name="custom_layout_update" type="xsd:string" minOccurs="0" />
                    <element name="options_container" type="xsd:string" minOccurs="0" />
                    <element name="additional_attributes" type="typens:associativeArray" minOccurs="0" />
                </all>
            </complexType>
        </schema>
    </types>
    <message name="importexportFooRequest">
        <part name="sessionId" type="xsd:string" />
    </message>
    <message name="importexportFooResponse">
        <part name="result" type="typens:boolean" />
    </message>
    <portType name="{{var wsdl.handler}}PortType">
        <operation name="importexportFoo">
            <documentation>ImportExport Foo</documentation>
            <input message="typens:importexportFooRequest" />
            <output message="typens:importexportFooResponse" />
        </operation>
    </portType>
    <binding name="{{var wsdl.handler}}Binding" type="typens:{{var wsdl.handler}}PortType">
        <soap:binding style="rpc" transport="http://schemas.xmlsoap.org/soap/http" />
        <operation name="importexportFoo">
            <soap:operation soapAction="urn:{{var wsdl.handler}}Action" />
            <input>
                <soap:body namespace="urn:{{var wsdl.name}}" use="encoded" encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" />
            </input>
            <output>
                <soap:body namespace="urn:{{var wsdl.name}}" use="encoded" encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" />
            </output>
        </operation>
    </binding>
</definitions>

/app/code/local/Namespace/ImportExport/Model/Api.php

<?php
class Namespace_ImportExport_Model_Api extends Mage_Api_Model_Resource_Abstract
{
    /**
     * Returns version of the installed magento
     * @return String
     */

    public function foo() {
        return true;
    }
}
?>

/app/code/local/Namespace/ImportExport/Model/API/V2.php

<?php
class Namespace_ImportExport_Model_Api_V2 extends Namespace_ImportExport_Model_Api
{
    public function foo() {
        return true;
    }
}
?>

And I make the call, like so...

$fclient = new SoapClient($config['from']['soap_url']);
$fsession = $fclient->login($config['from']['username'], $config['from']['api_key']);
var_dump($fclient->importexportFoo($fsession));

This to my knowledge is the bare necessities to get my custom api V2 module working. So what could I possibly be doing wrong ?

I am getting this for an error

Function ("importexportFoo") is not a valid method for this service

I've just had this kind of issue.

Check the value of $config['from']['soap_url'] when making the API call. If the value looks like http://example.com/api/soap?wsdlthen you are still making a call to V1. Update it to look like this http://example.com/api/v2_soap/?wsdl.