You'd need to retrieve the Data Extension object using a SimpleFilterPart - it supports the 'like' operator, something like this...
SOAP Example
<Envelope xmlns="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<Header>
<Security xmlns="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd">
<UsernameToken>
<Username>{{Username}}</Username>
<Password>{{Password}}</Password>
</UsernameToken>
</Security>
</Header>
<Body xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<RetrieveRequestMsg xmlns="http://exacttarget.com/wsdl/partnerAPI">
<RetrieveRequest>
<ObjectType>DataExtension</ObjectType>
<Properties>ObjectID</Properties>
<Properties>CustomerKey</Properties>
<Properties>Name</Properties>
<Properties>IsSendable</Properties>
<Properties>SendableSubscriberField.Name</Properties>
<Filter xsi:type="SimpleFilterPart">
<Property>Name</Property>
<SimpleOperator>like</SimpleOperator>
<Value>ctiv</Value>
</Filter>
</RetrieveRequest>
</RetrieveRequestMsg>
</Body>
</Envelope>
Returns...
<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing" xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd" xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd">
<soap:Header>
<wsa:Action>RetrieveResponse</wsa:Action>
<wsa:MessageID>urn:uuid:b1cb2645-c4c2-4dca-8a0a-1d004c1fe50a</wsa:MessageID>
<wsa:RelatesTo>urn:uuid:1be2f352-ce3f-4ba9-b24a-43b040a25a53</wsa:RelatesTo>
<wsa:To>http://schemas.xmlsoap.org/ws/2004/08/addressing/role/anonymous</wsa:To>
<wsse:Security>
<wsu:Timestamp wsu:Id="Timestamp-9e5b820f-32b0-4f1d-8b0b-99373eb56321">
<wsu:Created>2017-08-07T12:33:30Z</wsu:Created>
<wsu:Expires>2017-08-07T12:38:30Z</wsu:Expires>
</wsu:Timestamp>
</wsse:Security>
</soap:Header>
<soap:Body>
<RetrieveResponseMsg xmlns="http://exacttarget.com/wsdl/partnerAPI">
<OverallStatus>OK</OverallStatus>
<RequestID>b872a681-e291-4df8-b5cd-86178c4b915d</RequestID>
<Results xsi:type="DataExtension">
<PartnerKey xsi:nil="true" />
<ObjectID>fd32e4b5-00aa-e611-8c4c-00110a687a79</ObjectID>
<CustomerKey>PREDICTIVE_SCORES</CustomerKey>
<Name>PREDICTIVE_SCORES</Name>
<IsSendable>false</IsSendable>
</Results>
<Results xsi:type="DataExtension">
<PartnerKey xsi:nil="true" />
<ObjectID>0c6e94d9-427b-e711-80cb-1402ec723e3c</ObjectID>
<CustomerKey>ActivityInstance</CustomerKey>
<Name>ActivityInstance</Name>
<IsSendable>false</IsSendable>
</Results>
<Results xsi:type="DataExtension">
<PartnerKey xsi:nil="true" />
<ObjectID>136e94d9-427b-e711-80cb-1402ec723e3c</ObjectID>
<CustomerKey>Activity</CustomerKey>
<Name>Activity</Name>
<IsSendable>false</IsSendable>
</Results>
</RetrieveResponseMsg>
</soap:Body>
</soap:Envelope>
PHP Example
I never touch the SDKs, but PHP should look like this...
require('ET_Client.php');
$myclient = new ET_Client();
$dataextension = new ET_DataExtension();
$dataextension.filter = array('Property' => 'Name','SimpleOperator' => 'like','Value' => 'ctiv');
$dataextension->authStub = $myclient;
$response = $dataextension->get();
print_r($response);
Note:
The above examples do the equivalent of a SQL "LIKE ('%ctiv%')" and not "LIKE ('ctiv%')". For testing just the ending of the Name of the Data Extension, you would need to retrieve all DEs and loop through them all evaluating each on the client-side, as @Eliot Harper states.